diff --git a/Analyser/Static/Acorn/Disk.cpp b/Analyser/Static/Acorn/Disk.cpp
index 220f6d5c96..9b1516381f 100644
--- a/Analyser/Static/Acorn/Disk.cpp
+++ b/Analyser/Static/Acorn/Disk.cpp
@@ -19,10 +19,10 @@ using namespace Analyser::Static::Acorn;
 std::unique_ptr<Catalogue> Analyser::Static::Acorn::GetDFSCatalogue(const std::shared_ptr<Storage::Disk::Disk> &disk) {
 	// c.f. http://beebwiki.mdfs.net/Acorn_DFS_disc_format
 	auto catalogue = std::make_unique<Catalogue>();
-	Storage::Encodings::MFM::Parser parser(false, disk);
+	Storage::Encodings::MFM::Parser parser(Storage::Encodings::MFM::Density::Single, disk);
 
-	const Storage::Encodings::MFM::Sector *const names = parser.get_sector(0, 0, 0);
-	const Storage::Encodings::MFM::Sector *const details = parser.get_sector(0, 0, 1);
+	const Storage::Encodings::MFM::Sector *const names = parser.sector(0, 0, 0);
+	const Storage::Encodings::MFM::Sector *const details = parser.sector(0, 0, 1);
 
 	if(!names || !details) return nullptr;
 	if(names->samples.empty() || details->samples.empty()) return nullptr;
@@ -65,7 +65,7 @@ std::unique_ptr<Catalogue> Analyser::Static::Acorn::GetDFSCatalogue(const std::s
 			uint8_t track = uint8_t(start_sector / 10);
 			start_sector++;
 
-			Storage::Encodings::MFM::Sector *next_sector = parser.get_sector(0, track, sector);
+			const Storage::Encodings::MFM::Sector *next_sector = parser.sector(0, track, sector);
 			if(!next_sector) break;
 
 			long length_from_sector = std::min(data_length, 256l);
@@ -84,15 +84,15 @@ std::unique_ptr<Catalogue> Analyser::Static::Acorn::GetDFSCatalogue(const std::s
 */
 std::unique_ptr<Catalogue> Analyser::Static::Acorn::GetADFSCatalogue(const std::shared_ptr<Storage::Disk::Disk> &disk) {
 	auto catalogue = std::make_unique<Catalogue>();
-	Storage::Encodings::MFM::Parser parser(true, disk);
+	Storage::Encodings::MFM::Parser parser(Storage::Encodings::MFM::Density::Double, disk);
 
-	Storage::Encodings::MFM::Sector *free_space_map_second_half = parser.get_sector(0, 0, 1);
+	const Storage::Encodings::MFM::Sector *free_space_map_second_half = parser.sector(0, 0, 1);
 	if(!free_space_map_second_half) return nullptr;
 
 	std::vector<uint8_t> root_directory;
 	root_directory.reserve(5 * 256);
 	for(uint8_t c = 2; c < 7; c++) {
-		const Storage::Encodings::MFM::Sector *const sector = parser.get_sector(0, 0, c);
+		const Storage::Encodings::MFM::Sector *const sector = parser.sector(0, 0, c);
 		if(!sector) return nullptr;
 		root_directory.insert(root_directory.end(), sector->samples[0].begin(), sector->samples[0].end());
 	}
@@ -166,7 +166,7 @@ std::unique_ptr<Catalogue> Analyser::Static::Acorn::GetADFSCatalogue(const std::
 
 		new_file.data.reserve(size);
 		while(new_file.data.size() < size) {
-			const Storage::Encodings::MFM::Sector *const sector = parser.get_sector(start_sector / (80 * 16), (start_sector / 16) % 80, start_sector % 16);
+			const Storage::Encodings::MFM::Sector *const sector = parser.sector(start_sector / (80 * 16), (start_sector / 16) % 80, start_sector % 16);
 			if(!sector) break;
 
 			const auto length_from_sector = std::min(size - new_file.data.size(), sector->samples[0].size());
diff --git a/Analyser/Static/AmstradCPC/StaticAnalyser.cpp b/Analyser/Static/AmstradCPC/StaticAnalyser.cpp
index 2ca6924b6b..842371fe2d 100644
--- a/Analyser/Static/AmstradCPC/StaticAnalyser.cpp
+++ b/Analyser/Static/AmstradCPC/StaticAnalyser.cpp
@@ -159,8 +159,8 @@ void InspectCatalogue(
 }
 
 bool CheckBootSector(const std::shared_ptr<Storage::Disk::Disk> &disk, const std::unique_ptr<Analyser::Static::AmstradCPC::Target> &target) {
-	Storage::Encodings::MFM::Parser parser(true, disk);
-	Storage::Encodings::MFM::Sector *boot_sector = parser.get_sector(0, 0, 0x41);
+	Storage::Encodings::MFM::Parser parser(Storage::Encodings::MFM::Density::Double, disk);
+	const Storage::Encodings::MFM::Sector *boot_sector = parser.sector(0, 0, 0x41);
 	if(boot_sector != nullptr && !boot_sector->samples.empty() && boot_sector->samples[0].size() == 512) {
 		// Check that the first 64 bytes of the sector aren't identical; if they are then probably
 		// this disk was formatted and the filler byte never replaced.
diff --git a/Analyser/Static/Commodore/Disk.cpp b/Analyser/Static/Commodore/Disk.cpp
index d83d2a54ce..e759a636f6 100644
--- a/Analyser/Static/Commodore/Disk.cpp
+++ b/Analyser/Static/Commodore/Disk.cpp
@@ -37,7 +37,7 @@ class CommodoreGCRParser: public Storage::Disk::Controller {
 
 			@returns a sector if one was found; @c nullptr otherwise.
 		*/
-		std::shared_ptr<Sector> get_sector(uint8_t track, uint8_t sector) {
+		std::shared_ptr<Sector> sector(uint8_t track, uint8_t sector) {
 			int difference = int(track) - int(track_);
 			track_ = track;
 
@@ -182,7 +182,7 @@ std::vector<File> Analyser::Static::Commodore::GetFiles(const std::shared_ptr<St
 	uint8_t next_track = 18;
 	uint8_t next_sector = 1;
 	while(1) {
-		sector = parser.get_sector(next_track, next_sector);
+		sector = parser.sector(next_track, next_sector);
 		if(!sector) break;
 		directory.insert(directory.end(), sector->data.begin(), sector->data.end());
 		next_track = sector->data[0];
@@ -221,7 +221,7 @@ std::vector<File> Analyser::Static::Commodore::GetFiles(const std::shared_ptr<St
 
 		bool is_first_sector = true;
 		while(next_track) {
-			sector = parser.get_sector(next_track, next_sector);
+			sector = parser.sector(next_track, next_sector);
 			if(!sector) break;
 
 			next_track = sector->data[0];
diff --git a/Analyser/Static/FAT12/StaticAnalyser.cpp b/Analyser/Static/FAT12/StaticAnalyser.cpp
index 241705e334..dfca8053e1 100644
--- a/Analyser/Static/FAT12/StaticAnalyser.cpp
+++ b/Analyser/Static/FAT12/StaticAnalyser.cpp
@@ -44,7 +44,7 @@ Analyser::Static::TargetList Analyser::Static::FAT12::GetTargets(const Media &me
 			Storage::Disk::track_serialisation(
 				*track_zero,
 				Storage::Encodings::MFM::MFMBitLength
-			), true);
+			), Storage::Encodings::MFM::Density::Double);
 
 	// If no sectors were found, assume this disk was either single density or high density, which both imply the PC.
 	if(sector_map.empty() || sector_map.size() > 10) {
diff --git a/Analyser/Static/Oric/StaticAnalyser.cpp b/Analyser/Static/Oric/StaticAnalyser.cpp
index 2077ec2658..273c01e9f6 100644
--- a/Analyser/Static/Oric/StaticAnalyser.cpp
+++ b/Analyser/Static/Oric/StaticAnalyser.cpp
@@ -85,7 +85,7 @@ bool is_microdisc(Storage::Encodings::MFM::Parser &parser) {
 	/*
 		The Microdisc boot sector is sector 2 of track 0 and contains a 23-byte signature.
 	*/
-	Storage::Encodings::MFM::Sector *sector = parser.get_sector(0, 0, 2);
+	const Storage::Encodings::MFM::Sector *sector = parser.sector(0, 0, 2);
 	if(!sector) return false;
 	if(sector->samples.empty()) return false;
 
@@ -108,7 +108,7 @@ bool is_400_loader(Storage::Encodings::MFM::Parser &parser, uint16_t range_start
 		use disassembly to test for likely matches.
 	*/
 
-	Storage::Encodings::MFM::Sector *sector = parser.get_sector(0, 0, 1);
+	const Storage::Encodings::MFM::Sector *sector = parser.sector(0, 0, 1);
 	if(!sector) return false;
 	if(sector->samples.empty()) return false;
 
@@ -175,7 +175,7 @@ Analyser::Static::TargetList Analyser::Static::Oric::GetTargets(const Media &med
 		// 8-DOS is recognised by a dedicated Disk II analyser, so check only for Microdisc,
 		// Jasmin and BD-DOS formats here.
 		for(auto &disk: media.disks) {
-			Storage::Encodings::MFM::Parser parser(true, disk);
+			Storage::Encodings::MFM::Parser parser(Storage::Encodings::MFM::Density::Double, disk);
 
 			if(is_microdisc(parser)) {
 				target->disk_interface = Target::DiskInterface::Microdisc;
diff --git a/Analyser/Static/ZXSpectrum/StaticAnalyser.cpp b/Analyser/Static/ZXSpectrum/StaticAnalyser.cpp
index 0c21161e89..396c67f238 100644
--- a/Analyser/Static/ZXSpectrum/StaticAnalyser.cpp
+++ b/Analyser/Static/ZXSpectrum/StaticAnalyser.cpp
@@ -33,14 +33,14 @@ bool IsSpectrumTape(const std::shared_ptr<Storage::Tape::Tape> &tape) {
 }
 
 bool IsSpectrumDisk(const std::shared_ptr<Storage::Disk::Disk> &disk) {
-	Storage::Encodings::MFM::Parser parser(true, disk);
+	Storage::Encodings::MFM::Parser parser(Storage::Encodings::MFM::Density::Double, disk);
 
 	// Get logical sector 1; the Spectrum appears to support various physical
 	// sectors as sector 1.
-	Storage::Encodings::MFM::Sector *boot_sector = nullptr;
+	const Storage::Encodings::MFM::Sector *boot_sector = nullptr;
 	uint8_t sector_mask = 0;
 	while(!boot_sector) {
-		boot_sector = parser.get_sector(0, 0, sector_mask + 1);
+		boot_sector = parser.sector(0, 0, sector_mask + 1);
 		sector_mask += 0x40;
 		if(!sector_mask) break;
 	}
diff --git a/Machines/PCCompatible/PCCompatible.cpp b/Machines/PCCompatible/PCCompatible.cpp
index 76db9c97ae..dd0cb875e2 100644
--- a/Machines/PCCompatible/PCCompatible.cpp
+++ b/Machines/PCCompatible/PCCompatible.cpp
@@ -34,8 +34,7 @@
 #include "../../Outputs/Speaker/Implementation/LowpassSpeaker.hpp"
 
 #include "../../Storage/Disk/Track/TrackSerialiser.hpp"
-#include "../../Storage/Disk/Encodings/MFM/Constants.hpp"
-#include "../../Storage/Disk/Encodings/MFM/SegmentParser.hpp"
+#include "../../Storage/Disk/Encodings/MFM/Parser.hpp"
 
 #include "../AudioProducer.hpp"
 #include "../KeyboardMachine.hpp"
@@ -150,50 +149,32 @@ class FloppyController {
 						auto target = decoder_.geometry();
 						bool complete = false;
 						while(!complete) {
-							bool found_sector = false;
-
-							for(auto &pair: drives_[decoder_.target().drive].sectors(decoder_.target().head)) {
-								// TODO: I suspect that not all these fields are tested for equality.
-								if(
-									(pair.second.address.track == target.cylinder) &&
-									(pair.second.address.sector == target.sector) &&
-									(pair.second.address.side == target.head) &&
-									(pair.second.size == target.size) &&
-									(pair.second.is_deleted == (decoder_.command() == Command::ReadDeletedData))
-								) {
-									found_sector = true;
-									bool wrote_in_full = true;
-
-									for(int c = 0; c < 128 << target.size; c++) {
-										const auto access_result = dma_.write(2, pair.second.samples[0].data()[c]);
-										switch(access_result) {
-											default: break;
-											case AccessResult::NotAccepted:
-												complete = true;
-												wrote_in_full = false;
-											break;
-											case AccessResult::AcceptedWithEOP:
-												complete = true;
-											break;
-										}
-										if(access_result != AccessResult::Accepted) {
-											break;
-										}
-									}
-
-									if(!wrote_in_full) {
-										status_.set(Intel::i8272::Status1::OverRun);
-										status_.set(Intel::i8272::Status0::AbnormalTermination);
+							const auto sector = drives_[decoder_.target().drive].sector(target.head, target.sector);
+
+							if(sector) {
+								// TODO: I _think_ I'm supposed to validate the rest of the address here?
+
+								for(int c = 0; c < 128 << target.size; c++) {
+									const auto access_result = dma_.write(2, sector->samples[0].data()[c]);
+									switch(access_result) {
+										// Default: keep going.
+										default: continue;
+
+										// Anything else: update flags and exit.
+										case AccessResult::NotAccepted:
+											complete = true;
+											status_.set(Intel::i8272::Status1::OverRun);
+											status_.set(Intel::i8272::Status0::AbnormalTermination);
+										break;
+										case AccessResult::AcceptedWithEOP:
+											complete = true;
 										break;
 									}
-
-									++target.sector;	// TODO: multitrack?
-
 									break;
 								}
-							}
 
-							if(!found_sector) {
+								++target.sector;	// TODO: multitrack?
+							} else {
 								status_.set(Intel::i8272::Status1::EndOfCylinder);
 								status_.set(Intel::i8272::Status0::AbnormalTermination);
 								break;
@@ -342,58 +323,19 @@ class FloppyController {
 				bool exists = true;
 
 				bool has_disk() const {
-					return bool(disk);
+					return static_cast<bool>(parser_);
 				}
 
 				void set_disk(std::shared_ptr<Storage::Disk::Disk> image) {
-					disk = image;
-					cached.clear();
+					parser_ = std::make_unique<Storage::Encodings::MFM::Parser>(image);
 				}
 
-				Storage::Encodings::MFM::SectorMap &sectors(bool side) {
-					if(cached.track == track && cached.side == side) {
-						return cached.sectors;
-					}
-
-					cached.track = track;
-					cached.side = side;
-					cached.sectors.clear();
-
-					if(!disk) {
-						return cached.sectors;
-					}
-
-					auto raw_track = disk->get_track_at_position(
-						Storage::Disk::Track::Address(
-							side,
-							Storage::Disk::HeadPosition(track)
-						)
-					);
-					if(!raw_track) {
-						return cached.sectors;
-					}
-
-					const bool is_double_density = true;	// TODO: use MFM flag here.
-					auto serialisation = Storage::Disk::track_serialisation(
-						*raw_track,
-						is_double_density ? Storage::Encodings::MFM::MFMBitLength : Storage::Encodings::MFM::FMBitLength
-					);
-					cached.sectors = Storage::Encodings::MFM::sectors_from_segment(std::move(serialisation), is_double_density);
-					return cached.sectors;
+				const Storage::Encodings::MFM::Sector *sector(int head, uint8_t sector) {
+					return parser_ ? parser_->sector(head, track, sector) : nullptr;
 				}
 
 			private:
-				struct {
-					uint8_t track = 0xff;
-					bool side;
-					Storage::Encodings::MFM::SectorMap sectors;
-
-					void clear() {
-						track = 0xff;
-						sectors.clear();
-					}
-				} cached;
-				std::shared_ptr<Storage::Disk::Disk> disk;
+				std::unique_ptr<Storage::Encodings::MFM::Parser> parser_;
 
 		} drives_[4];
 
diff --git a/Storage/Disk/Controller/MFMDiskController.cpp b/Storage/Disk/Controller/MFMDiskController.cpp
index ef3122291f..c6d57a8c0c 100644
--- a/Storage/Disk/Controller/MFMDiskController.cpp
+++ b/Storage/Disk/Controller/MFMDiskController.cpp
@@ -32,7 +32,7 @@ void MFMController::set_is_double_density(bool is_double_density) {
 	bit_length.clock_rate = is_double_density ? 500000 : 250000;
 	set_expected_bit_length(bit_length);
 
-	shifter_.set_is_double_density(is_double_density);
+	shifter_.set_is_mfm(is_double_density);
 }
 
 bool MFMController::get_is_double_density() {
diff --git a/Storage/Disk/DiskImage/Formats/AcornADF.cpp b/Storage/Disk/DiskImage/Formats/AcornADF.cpp
index b7c4fd2d39..57e333c199 100644
--- a/Storage/Disk/DiskImage/Formats/AcornADF.cpp
+++ b/Storage/Disk/DiskImage/Formats/AcornADF.cpp
@@ -39,7 +39,7 @@ AcornADF::AcornADF(const std::string &file_name) : MFMSectorDump(file_name) {
 	head_count_ = 1 + (file_.stats().st_size > sectors_per_track * sizeT(128 << sector_size) * 80);
 
 	// Announce disk geometry.
-	set_geometry(sectors_per_track, sector_size, 0, true);
+	set_geometry(sectors_per_track, sector_size, 0, Encodings::MFM::Density::Double);
 }
 
 HeadPosition AcornADF::get_maximum_head_position() {
diff --git a/Storage/Disk/DiskImage/Formats/CPCDSK.cpp b/Storage/Disk/DiskImage/Formats/CPCDSK.cpp
index ac81e5556f..28a0b9c416 100644
--- a/Storage/Disk/DiskImage/Formats/CPCDSK.cpp
+++ b/Storage/Disk/DiskImage/Formats/CPCDSK.cpp
@@ -214,7 +214,11 @@ std::shared_ptr<Track> CPCDSK::get_track_at_position(::Storage::Disk::Track::Add
 	}
 
 	// TODO: FM encoding, data rate?
-	return Storage::Encodings::MFM::GetMFMTrackWithSectors(sectors, track->gap3_length, track->filler_byte);
+	return Storage::Encodings::MFM::TrackWithSectors(
+		Storage::Encodings::MFM::Density::Double,
+		sectors,
+		track->gap3_length,
+		track->filler_byte);
 }
 
 void CPCDSK::set_tracks(const std::map<::Storage::Disk::Track::Address, std::shared_ptr<::Storage::Disk::Track>> &tracks) {
@@ -225,7 +229,7 @@ void CPCDSK::set_tracks(const std::map<::Storage::Disk::Track::Address, std::sha
 		std::map<std::size_t, Storage::Encodings::MFM::Sector> sectors =
 			Storage::Encodings::MFM::sectors_from_segment(
 				Storage::Disk::track_serialisation(*pair.second, is_double_density ? Storage::Encodings::MFM::MFMBitLength : Storage::Encodings::MFM::FMBitLength),
-				is_double_density);
+				Storage::Encodings::MFM::Density::Double);
 
 		// Find slot for track, making it if neccessary.
 		const std::size_t chronological_track = index_for_track(pair.first);
diff --git a/Storage/Disk/DiskImage/Formats/FAT12.cpp b/Storage/Disk/DiskImage/Formats/FAT12.cpp
index 574e61c961..fc2d8b6dbb 100644
--- a/Storage/Disk/DiskImage/Formats/FAT12.cpp
+++ b/Storage/Disk/DiskImage/Formats/FAT12.cpp
@@ -41,7 +41,12 @@ FAT12::FAT12(const std::string &file_name) :
 	}
 	if(log_sector_size >= 5) throw Error::InvalidFormat;
 
-	set_geometry(sector_count_, log_sector_size, 1, true);
+	set_geometry(
+		sector_count_,
+		log_sector_size,
+		1,
+		sector_count_ > 10 ? Encodings::MFM::Density::High : Encodings::MFM::Density::Double
+	);
 }
 
 HeadPosition FAT12::get_maximum_head_position() {
diff --git a/Storage/Disk/DiskImage/Formats/IMD.cpp b/Storage/Disk/DiskImage/Formats/IMD.cpp
index 379fddaf5d..b94435a9a9 100644
--- a/Storage/Disk/DiskImage/Formats/IMD.cpp
+++ b/Storage/Disk/DiskImage/Formats/IMD.cpp
@@ -157,7 +157,13 @@ std::shared_ptr<::Storage::Disk::Track> IMD::get_track_at_position(::Storage::Di
 	// Mode also indicates data density, but I don't have a good strategy for reconciling that if
 	// it were to disagree with the density implied by the quantity of sectors. So a broad 'is it MFM' test is
 	// applied only.
-	return (mode >= 3) ?
-		Storage::Encodings::MFM::GetMFMTrackWithSectors(sectors) :
-		Storage::Encodings::MFM::GetFMTrackWithSectors(sectors);
+	using namespace Storage::Encodings::MFM;
+	if(mode < 3) {
+		return TrackWithSectors(Density::Single, sectors);
+	}
+	if(sector_size * sector_count >= 6912) {
+		return TrackWithSectors(Density::High, sectors);
+	} else {
+		return TrackWithSectors(Density::Double, sectors);
+	}
 }
diff --git a/Storage/Disk/DiskImage/Formats/MFMSectorDump.cpp b/Storage/Disk/DiskImage/Formats/MFMSectorDump.cpp
index 9f629b9869..f0ce69d279 100644
--- a/Storage/Disk/DiskImage/Formats/MFMSectorDump.cpp
+++ b/Storage/Disk/DiskImage/Formats/MFMSectorDump.cpp
@@ -14,10 +14,10 @@ using namespace Storage::Disk;
 
 MFMSectorDump::MFMSectorDump(const std::string &file_name) : file_(file_name) {}
 
-void MFMSectorDump::set_geometry(int sectors_per_track, uint8_t sector_size, uint8_t first_sector, bool is_double_density) {
+void MFMSectorDump::set_geometry(int sectors_per_track, uint8_t sector_size, uint8_t first_sector, Encodings::MFM::Density density) {
 	sectors_per_track_ = sectors_per_track;
 	sector_size_ = sector_size;
-	is_double_density_ = is_double_density;
+	density_ = density;
 	first_sector_ = first_sector;
 }
 
@@ -34,7 +34,14 @@ std::shared_ptr<Track> MFMSectorDump::get_track_at_position(Track::Address addre
 		file_.read(sectors, sizeof(sectors));
 	}
 
-	return track_for_sectors(sectors, sectors_per_track_, uint8_t(address.position.as_int()), uint8_t(address.head), first_sector_, sector_size_, is_double_density_);
+	return track_for_sectors(
+		sectors,
+		sectors_per_track_,
+		uint8_t(address.position.as_int()),
+		uint8_t(address.head),
+		first_sector_,
+		sector_size_,
+		density_);
 }
 
 void MFMSectorDump::set_tracks(const std::map<Track::Address, std::shared_ptr<Track>> &tracks) {
@@ -44,7 +51,13 @@ void MFMSectorDump::set_tracks(const std::map<Track::Address, std::shared_ptr<Tr
 	// in one loop, then write in another.
 
 	for(const auto &track : tracks) {
-		decode_sectors(*track.second, parsed_track, first_sector_, first_sector_ + uint8_t(sectors_per_track_-1), sector_size_, is_double_density_);
+		decode_sectors(
+			*track.second,
+			parsed_track,
+			first_sector_,
+			first_sector_ + uint8_t(sectors_per_track_-1),
+			sector_size_,
+			density_);
 		const long file_offset = get_file_offset_for_position(track.first);
 
 		std::lock_guard lock_guard(file_.get_file_access_mutex());
diff --git a/Storage/Disk/DiskImage/Formats/MFMSectorDump.hpp b/Storage/Disk/DiskImage/Formats/MFMSectorDump.hpp
index a164f874b6..21286d6acc 100644
--- a/Storage/Disk/DiskImage/Formats/MFMSectorDump.hpp
+++ b/Storage/Disk/DiskImage/Formats/MFMSectorDump.hpp
@@ -11,6 +11,7 @@
 
 #include "../DiskImage.hpp"
 #include "../../../FileHolder.hpp"
+#include "../../Encodings/MFM/Constants.hpp"
 
 #include <string>
 
@@ -29,14 +30,14 @@ class MFMSectorDump: public DiskImage {
 
 	protected:
 		Storage::FileHolder file_;
-		void set_geometry(int sectors_per_track, uint8_t sector_size, uint8_t first_sector, bool is_double_density);
+		void set_geometry(int sectors_per_track, uint8_t sector_size, uint8_t first_sector, Encodings::MFM::Density density);
 
 	private:
 		virtual long get_file_offset_for_position(Track::Address address) = 0;
 
 		int sectors_per_track_ = 0;
 		uint8_t sector_size_ = 0;
-		bool is_double_density_ = true;
+		Encodings::MFM::Density density_ = Encodings::MFM::Density::Single;
 		uint8_t first_sector_ = 0;
 };
 
diff --git a/Storage/Disk/DiskImage/Formats/MSA.cpp b/Storage/Disk/DiskImage/Formats/MSA.cpp
index 2da6976052..a2917d4710 100644
--- a/Storage/Disk/DiskImage/Formats/MSA.cpp
+++ b/Storage/Disk/DiskImage/Formats/MSA.cpp
@@ -84,7 +84,7 @@ std::shared_ptr<::Storage::Disk::Track> MSA::get_track_at_position(::Storage::Di
 
 	const auto &track = uncompressed_tracks_[size_t(position - starting_track_) * size_t(sides_) + size_t(address.head)];
 	assert(!track.empty());
-	return track_for_sectors(track.data(), sectors_per_track_, uint8_t(position), uint8_t(address.head), 1, 2, true);
+	return track_for_sectors(track.data(), sectors_per_track_, uint8_t(position), uint8_t(address.head), 1, 2, Storage::Encodings::MFM::Density::Double);
 }
 
 HeadPosition MSA::get_maximum_head_position() {
diff --git a/Storage/Disk/DiskImage/Formats/OricMFMDSK.cpp b/Storage/Disk/DiskImage/Formats/OricMFMDSK.cpp
index f7bd337446..9e4ec60603 100644
--- a/Storage/Disk/DiskImage/Formats/OricMFMDSK.cpp
+++ b/Storage/Disk/DiskImage/Formats/OricMFMDSK.cpp
@@ -119,7 +119,7 @@ void OricMFMDSK::set_tracks(const std::map<Track::Address, std::shared_ptr<Track
 	for(const auto &track : tracks) {
 		PCMSegment segment = Storage::Disk::track_serialisation(*track.second, Storage::Encodings::MFM::MFMBitLength);
 		Storage::Encodings::MFM::Shifter shifter;
-		shifter.set_is_double_density(true);
+		shifter.set_is_mfm(true);
 		shifter.set_should_obey_syncs(true);
 		std::vector<uint8_t> parsed_track;
 		int size = 0;
diff --git a/Storage/Disk/DiskImage/Formats/PCBooter.cpp b/Storage/Disk/DiskImage/Formats/PCBooter.cpp
index 54e14a8ea9..20701f572a 100644
--- a/Storage/Disk/DiskImage/Formats/PCBooter.cpp
+++ b/Storage/Disk/DiskImage/Formats/PCBooter.cpp
@@ -47,7 +47,8 @@ PCBooter::PCBooter(const std::string &file_name) :
 		break;
 	}
 
-	set_geometry(sector_count_, 2, 1, true);
+	// TODO: probably single density, actually?
+	set_geometry(sector_count_, 2, 1, Encodings::MFM::Density::Double);
 
 	// TODO: check that an appropriate INT or similar is in the boot sector?
 	// Should probably factor out the "does this look like a PC boot sector?" test,
diff --git a/Storage/Disk/DiskImage/Formats/SSD.cpp b/Storage/Disk/DiskImage/Formats/SSD.cpp
index 455fddc4a7..b312e6ac44 100644
--- a/Storage/Disk/DiskImage/Formats/SSD.cpp
+++ b/Storage/Disk/DiskImage/Formats/SSD.cpp
@@ -29,7 +29,7 @@ SSD::SSD(const std::string &file_name) : MFMSectorDump(file_name) {
 	if(track_count_ < 40) track_count_ = 40;
 	else if(track_count_ < 80) track_count_ = 80;
 
-	set_geometry(sectors_per_track, sector_size, 0, false);
+	set_geometry(sectors_per_track, sector_size, 0, Encodings::MFM::Density::Single);
 }
 
 HeadPosition SSD::get_maximum_head_position() {
diff --git a/Storage/Disk/DiskImage/Formats/STX.cpp b/Storage/Disk/DiskImage/Formats/STX.cpp
index 6aafc04fd8..4c26038edc 100644
--- a/Storage/Disk/DiskImage/Formats/STX.cpp
+++ b/Storage/Disk/DiskImage/Formats/STX.cpp
@@ -136,7 +136,7 @@ class TrackConstructor {
 					using Shifter = Storage::Encodings::MFM::Shifter;
 					Shifter shifter;
 					shifter.set_should_obey_syncs(true);
-					shifter.set_is_double_density(true);
+					shifter.set_is_mfm(true);
 
 					result.emplace_back();
 
@@ -469,7 +469,7 @@ std::shared_ptr<::Storage::Disk::Track> STX::get_track_at_position(::Storage::Di
 	// If this is a trivial .ST-style sector dump, life is easy.
 	if(!(flags & 1)) {
 		const auto sector_contents = file_.read(sector_count * 512);
-		return track_for_sectors(sector_contents.data(), sector_count, uint8_t(address.position.as_int()), uint8_t(address.head), 1, 2, true);
+		return track_for_sectors(sector_contents.data(), sector_count, uint8_t(address.position.as_int()), uint8_t(address.head), 1, 2, Storage::Encodings::MFM::Density::Double);
 	}
 
 	// Grab sector records, if provided.
diff --git a/Storage/Disk/DiskImage/Formats/Utility/ImplicitSectors.cpp b/Storage/Disk/DiskImage/Formats/Utility/ImplicitSectors.cpp
index fa6993e747..b18242a5b6 100644
--- a/Storage/Disk/DiskImage/Formats/Utility/ImplicitSectors.cpp
+++ b/Storage/Disk/DiskImage/Formats/Utility/ImplicitSectors.cpp
@@ -18,7 +18,15 @@
 
 using namespace Storage::Disk;
 
-std::shared_ptr<Track> Storage::Disk::track_for_sectors(const uint8_t *const source, int number_of_sectors, uint8_t track, uint8_t side, uint8_t first_sector, uint8_t size, bool is_double_density) {
+std::shared_ptr<Track> Storage::Disk::track_for_sectors(
+	const uint8_t *const source,
+	int number_of_sectors,
+	uint8_t track,
+	uint8_t side,
+	uint8_t first_sector,
+	uint8_t size,
+	Storage::Encodings::MFM::Density density
+) {
 	std::vector<Storage::Encodings::MFM::Sector> sectors;
 
 	size_t byte_size = size_t(128 << size);
@@ -39,17 +47,27 @@ std::shared_ptr<Track> Storage::Disk::track_for_sectors(const uint8_t *const sou
 	}
 
 	if(!sectors.empty()) {
-		return is_double_density ? Storage::Encodings::MFM::GetMFMTrackWithSectors(sectors) : Storage::Encodings::MFM::GetFMTrackWithSectors(sectors);
+		return TrackWithSectors(density, sectors);
 	}
 
 	return nullptr;
 }
 
-void Storage::Disk::decode_sectors(Track &track, uint8_t *const destination, uint8_t first_sector, uint8_t last_sector, uint8_t sector_size, bool is_double_density) {
+void Storage::Disk::decode_sectors(
+	const Track &track,
+	uint8_t *const destination,
+	uint8_t first_sector,
+	uint8_t last_sector,
+	uint8_t sector_size,
+	Storage::Encodings::MFM::Density density
+) {
 	std::map<std::size_t, Storage::Encodings::MFM::Sector> sectors =
 		Storage::Encodings::MFM::sectors_from_segment(
-			Storage::Disk::track_serialisation(track, is_double_density ? Storage::Encodings::MFM::MFMBitLength : Storage::Encodings::MFM::FMBitLength),
-			is_double_density);
+			Storage::Disk::track_serialisation(
+				track,
+				Storage::Encodings::MFM::bit_length(density)
+			),
+			density);
 
 	std::size_t byte_size = size_t(128 << sector_size);
 	for(const auto &pair : sectors) {
diff --git a/Storage/Disk/DiskImage/Formats/Utility/ImplicitSectors.hpp b/Storage/Disk/DiskImage/Formats/Utility/ImplicitSectors.hpp
index 3714837d8e..d6db555c5a 100644
--- a/Storage/Disk/DiskImage/Formats/Utility/ImplicitSectors.hpp
+++ b/Storage/Disk/DiskImage/Formats/Utility/ImplicitSectors.hpp
@@ -13,10 +13,13 @@
 #include <memory>
 #include <vector>
 
+#include "../../../Encodings/MFM/Encoder.hpp"
+
+
 namespace Storage::Disk {
 
-std::shared_ptr<Track> track_for_sectors(const uint8_t *source, int number_of_sectors, uint8_t track, uint8_t side, uint8_t first_sector, uint8_t size, bool is_double_density);
-void decode_sectors(Track &track, uint8_t *destination, uint8_t first_sector, uint8_t last_sector, uint8_t sector_size, bool is_double_density);
+std::shared_ptr<Track> track_for_sectors(const uint8_t *source, int number_of_sectors, uint8_t track, uint8_t side, uint8_t first_sector, uint8_t size, Storage::Encodings::MFM::Density density);
+void decode_sectors(const Track &track, uint8_t *destination, uint8_t first_sector, uint8_t last_sector, uint8_t sector_size, Storage::Encodings::MFM::Density density);
 
 }
 
diff --git a/Storage/Disk/Encodings/MFM/Constants.hpp b/Storage/Disk/Encodings/MFM/Constants.hpp
index 011af4dc9c..838e7d34e4 100644
--- a/Storage/Disk/Encodings/MFM/Constants.hpp
+++ b/Storage/Disk/Encodings/MFM/Constants.hpp
@@ -13,6 +13,14 @@
 
 namespace Storage::Encodings::MFM {
 
+enum class Density {
+	Single, Double, High
+};
+
+constexpr bool is_mfm(Density density) {
+	return density != Density::Single;
+}
+
 const uint8_t IndexAddressByte			= 0xfc;
 const uint8_t IDAddressByte				= 0xfe;
 const uint8_t DataAddressByte			= 0xfb;
@@ -30,9 +38,18 @@ const uint16_t MFMPostSyncCRCValue		= 0xcdb4;	// the value the CRC generator sho
 const uint8_t MFMIndexSyncByteValue		= 0xc2;
 const uint8_t MFMSyncByteValue			= 0xa1;
 
+const Time HDMFMBitLength				= Time(1, 200000);
 const Time MFMBitLength					= Time(1, 100000);
 const Time FMBitLength					= Time(1, 50000);
 
+constexpr Time bit_length(Density density) {
+	switch(density) {
+		case Density::Single:	return FMBitLength;
+		case Density::Double:	return MFMBitLength;
+		case Density::High:		return HDMFMBitLength;
+	}
+}
+
 }
 
 #endif /* Constants_h */
diff --git a/Storage/Disk/Encodings/MFM/Encoder.cpp b/Storage/Disk/Encodings/MFM/Encoder.cpp
index fbd5bbf410..0379fadab5 100644
--- a/Storage/Disk/Encodings/MFM/Encoder.cpp
+++ b/Storage/Disk/Encodings/MFM/Encoder.cpp
@@ -18,6 +18,62 @@
 
 using namespace Storage::Encodings::MFM;
 
+namespace {
+
+std::vector<const Sector *> sector_pointers(const std::vector<Sector> &sectors) {
+	std::vector<const Sector *> pointers;
+	for(const Sector &sector: sectors) {
+		pointers.push_back(&sector);
+	}
+	return pointers;
+}
+
+template <Density density> struct Defaults;
+template <> struct Defaults<Density::Single> {
+	static constexpr size_t expected_track_bytes = 6250;
+
+	static constexpr size_t post_index_address_mark_bytes = 26;
+	static constexpr uint8_t post_index_address_mark_value = 0xff;
+
+	static constexpr size_t pre_address_mark_bytes = 6;
+	static constexpr size_t post_address_address_mark_bytes = 11;
+	static constexpr uint8_t post_address_address_mark_value = 0xff;
+
+	static constexpr size_t pre_data_mark_bytes = 6;
+	static constexpr size_t post_data_bytes = 27;
+	static constexpr uint8_t post_data_value = 0xff;
+};
+template <> struct Defaults<Density::Double> {
+	static constexpr size_t expected_track_bytes = 12500;
+
+	static constexpr size_t post_index_address_mark_bytes = 50;
+	static constexpr uint8_t post_index_address_mark_value = 0x4e;
+
+	static constexpr size_t pre_address_mark_bytes = 12;
+	static constexpr size_t post_address_address_mark_bytes = 22;
+	static constexpr uint8_t post_address_address_mark_value = 0x4e;
+
+	static constexpr size_t pre_data_mark_bytes = 12;
+	static constexpr size_t post_data_bytes = 54;
+	static constexpr uint8_t post_data_value = 0xff;
+};
+template <> struct Defaults<Density::High> {
+	static constexpr size_t expected_track_bytes = 25000;
+
+	static constexpr size_t post_index_address_mark_bytes = 50;
+	static constexpr uint8_t post_index_address_mark_value = 0x4e;
+
+	static constexpr size_t pre_address_mark_bytes = 12;
+	static constexpr size_t post_address_address_mark_bytes = 22;
+	static constexpr uint8_t post_address_address_mark_value = 0x4e;
+
+	static constexpr size_t pre_data_mark_bytes = 12;
+	static constexpr size_t post_data_bytes = 54;
+	static constexpr uint8_t post_data_value = 0xff;
+};
+
+}
+
 enum class SurfaceItem {
 	Mark,
 	Data
@@ -124,7 +180,7 @@ class FMEncoder: public Encoder {
 };
 
 template<class T> std::shared_ptr<Storage::Disk::Track>
-		GetTrackWithSectors(
+		GTrackWithSectors(
 			const std::vector<const Sector *> &sectors,
 			std::size_t post_index_address_mark_bytes, uint8_t post_index_address_mark_value,
 			std::size_t pre_address_mark_bytes,
@@ -281,58 +337,55 @@ void Encoder::add_crc(bool incorrectly) {
 	add_byte((crc_value & 0xff) ^ (incorrectly ? 1 : 0));
 }
 
-const std::size_t Storage::Encodings::MFM::DefaultSectorGapLength = std::numeric_limits<std::size_t>::max();
-
-static std::vector<const Sector *> sector_pointers(const std::vector<Sector> &sectors) {
-	std::vector<const Sector *> pointers;
-	for(const Sector &sector: sectors) {
-		pointers.push_back(&sector);
-	}
-	return pointers;
-}
-
-std::shared_ptr<Storage::Disk::Track> Storage::Encodings::MFM::GetFMTrackWithSectors(const std::vector<Sector> &sectors, std::size_t sector_gap_length, uint8_t sector_gap_filler_byte) {
-	return GetTrackWithSectors<FMEncoder>(
-		sector_pointers(sectors),
-		26, 0xff,
-		6,
-		11, sector_gap_filler_byte,
-		6,
-		(sector_gap_length != DefaultSectorGapLength) ? sector_gap_length : 27, 0xff,
-		6250);	// i.e. 250kbps (including clocks) * 60 = 15000kpm, at 300 rpm => 50 kbits/rotation => 6250 bytes/rotation
+namespace {
+template <Density density>
+std::shared_ptr<Storage::Disk::Track> TTrackWithSectors(
+	const std::vector<const Sector *> &sectors,
+	std::optional<std::size_t> sector_gap_length,
+	std::optional<uint8_t> sector_gap_filler_byte
+) {
+	using EncoderT = std::conditional_t<density == Density::Single, FMEncoder, MFMEncoder>;
+	return GTrackWithSectors<EncoderT>(
+		sectors,
+		Defaults<density>::post_index_address_mark_bytes,
+		Defaults<density>::post_index_address_mark_value,
+		Defaults<density>::pre_address_mark_bytes,
+		Defaults<density>::post_address_address_mark_bytes,
+		sector_gap_filler_byte ? *sector_gap_filler_byte : Defaults<density>::post_address_address_mark_value,
+		Defaults<density>::pre_data_mark_bytes,
+		sector_gap_length ? *sector_gap_length : Defaults<density>::post_data_bytes,
+		Defaults<density>::post_data_value,
+		Defaults<density>::expected_track_bytes
+	);
 }
 
-std::shared_ptr<Storage::Disk::Track> Storage::Encodings::MFM::GetFMTrackWithSectors(const std::vector<const Sector *> &sectors, std::size_t sector_gap_length, uint8_t sector_gap_filler_byte) {
-	return GetTrackWithSectors<FMEncoder>(
-		sectors,
-		26, 0xff,
-		6,
-		11, sector_gap_filler_byte,
-		6,
-		(sector_gap_length != DefaultSectorGapLength) ? sector_gap_length : 27, 0xff,
-		6250);	// i.e. 250kbps (including clocks) * 60 = 15000kpm, at 300 rpm => 50 kbits/rotation => 6250 bytes/rotation
 }
 
-std::shared_ptr<Storage::Disk::Track> Storage::Encodings::MFM::GetMFMTrackWithSectors(const std::vector<Sector> &sectors, std::size_t sector_gap_length, uint8_t sector_gap_filler_byte) {
-	return GetTrackWithSectors<MFMEncoder>(
+std::shared_ptr<Storage::Disk::Track> Storage::Encodings::MFM::TrackWithSectors(
+	Density density,
+	const std::vector<Sector> &sectors,
+	std::optional<std::size_t> sector_gap_length,
+	std::optional<uint8_t> sector_gap_filler_byte
+) {
+	return TrackWithSectors(
+		density,
 		sector_pointers(sectors),
-		50, 0x4e,
-		12,
-		22, sector_gap_filler_byte,
-		12,
-		(sector_gap_length != DefaultSectorGapLength) ? sector_gap_length : 54, 0xff,
-		12500);	// unintelligently: double the single-density bytes/rotation (or: 500kbps @ 300 rpm)
+		sector_gap_length,
+		sector_gap_filler_byte
+	);
 }
 
-std::shared_ptr<Storage::Disk::Track> Storage::Encodings::MFM::GetMFMTrackWithSectors(const std::vector<const Sector *> &sectors, std::size_t sector_gap_length, uint8_t sector_gap_filler_byte) {
-	return GetTrackWithSectors<MFMEncoder>(
-		sectors,
-		50, 0x4e,
-		12,
-		22, sector_gap_filler_byte,
-		12,
-		(sector_gap_length != DefaultSectorGapLength) ? sector_gap_length : 54, 0xff,
-		12500);	// unintelligently: double the single-density bytes/rotation (or: 500kbps @ 300 rpm)
+std::shared_ptr<Storage::Disk::Track> Storage::Encodings::MFM::TrackWithSectors(
+	Density density,
+	const std::vector<const Sector *> &sectors,
+	std::optional<std::size_t> sector_gap_length,
+	std::optional<uint8_t> sector_gap_filler_byte
+) {
+	switch(density) {
+		case Density::Single:	return TTrackWithSectors<Density::Single>(sectors, sector_gap_length, sector_gap_filler_byte);
+		case Density::Double:	return TTrackWithSectors<Density::Double>(sectors, sector_gap_length, sector_gap_filler_byte);
+		case Density::High:		return TTrackWithSectors<Density::High>(sectors, sector_gap_length, sector_gap_filler_byte);
+	}
 }
 
 std::unique_ptr<Encoder> Storage::Encodings::MFM::GetMFMEncoder(std::vector<bool> &target, std::vector<bool> *fuzzy_target) {
diff --git a/Storage/Disk/Encodings/MFM/Encoder.hpp b/Storage/Disk/Encodings/MFM/Encoder.hpp
index babec8b356..94ae4617f9 100644
--- a/Storage/Disk/Encodings/MFM/Encoder.hpp
+++ b/Storage/Disk/Encodings/MFM/Encoder.hpp
@@ -11,34 +11,34 @@
 
 #include <cstdint>
 #include <memory>
+#include <optional>
 #include <vector>
 
+#include "Constants.hpp"
 #include "Sector.hpp"
 #include "../../Track/Track.hpp"
 #include "../../../../Numeric/CRC.hpp"
 
 namespace Storage::Encodings::MFM {
 
-extern const std::size_t DefaultSectorGapLength;
 /*!
-	Converts a vector of sectors into a properly-encoded MFM track.
+	Converts a vector of sectors into a properly-encoded FM or MFM track.
 
 	@param sectors The sectors to write.
 	@param sector_gap_length If specified, sets the distance in whole bytes between each ID and its data.
 	@param sector_gap_filler_byte If specified, sets the value (unencoded) that is used to populate the gap between each ID and its data.
 */
-std::shared_ptr<Storage::Disk::Track> GetMFMTrackWithSectors(const std::vector<Sector> &sectors, std::size_t sector_gap_length = DefaultSectorGapLength, uint8_t sector_gap_filler_byte = 0x4e);
-std::shared_ptr<Storage::Disk::Track> GetMFMTrackWithSectors(const std::vector<const Sector *> &sectors, std::size_t sector_gap_length = DefaultSectorGapLength, uint8_t sector_gap_filler_byte = 0x4e);
-
-/*!
-	Converts a vector of sectors into a properly-encoded FM track.
-
-	@param sectors The sectors to write.
-	@param sector_gap_length If specified, sets the distance in whole bytes between each ID and its data.
-	@param sector_gap_filler_byte If specified, sets the value (unencoded) that is used to populate the gap between each ID and its data.
-*/
-std::shared_ptr<Storage::Disk::Track> GetFMTrackWithSectors(const std::vector<Sector> &sectors, std::size_t sector_gap_length = DefaultSectorGapLength, uint8_t sector_gap_filler_byte = 0xff);
-std::shared_ptr<Storage::Disk::Track> GetFMTrackWithSectors(const std::vector<const Sector *> &sectors, std::size_t sector_gap_length = DefaultSectorGapLength, uint8_t sector_gap_filler_byte = 0xff);
+std::shared_ptr<Storage::Disk::Track> TrackWithSectors(
+	Density density,
+	const std::vector<Sector> &sectors,
+	std::optional<std::size_t> sector_gap_length = std::nullopt,
+	std::optional<uint8_t> sector_gap_filler_byte = std::nullopt);
+
+std::shared_ptr<Storage::Disk::Track> TrackWithSectors(
+	Density density,
+	const std::vector<const Sector *> &sectors,
+	std::optional<std::size_t> sector_gap_length = std::nullopt,
+	std::optional<uint8_t> sector_gap_filler_byte = std::nullopt);
 
 class Encoder {
 	public:
diff --git a/Storage/Disk/Encodings/MFM/Parser.cpp b/Storage/Disk/Encodings/MFM/Parser.cpp
index 79907f2036..efc8510422 100644
--- a/Storage/Disk/Encodings/MFM/Parser.cpp
+++ b/Storage/Disk/Encodings/MFM/Parser.cpp
@@ -14,40 +14,58 @@
 
 using namespace Storage::Encodings::MFM;
 
-Parser::Parser(bool is_mfm, const std::shared_ptr<Storage::Disk::Disk> &disk) :
-		disk_(disk), is_mfm_(is_mfm) {}
+Parser::Parser(const std::shared_ptr<Storage::Disk::Disk> &disk) :
+		disk_(disk) {}
 
-void Parser::install_sectors_from_track(const Storage::Disk::Track::Address &address) {
+Parser::Parser(Density density, const std::shared_ptr<Storage::Disk::Disk> &disk) :
+		disk_(disk), density_(density) {}
+
+void Parser::install_track(const Storage::Disk::Track::Address &address) {
 	if(sectors_by_address_by_track_.find(address) != sectors_by_address_by_track_.end()) {
 		return;
 	}
 
-	std::shared_ptr<Storage::Disk::Track> track = disk_->get_track_at_position(address);
+	const auto track = disk_->get_track_at_position(address);
 	if(!track) {
 		return;
 	}
 
-	std::map<std::size_t, Sector> sectors = sectors_from_segment(
-		Storage::Disk::track_serialisation(*track, is_mfm_ ? MFMBitLength : FMBitLength),
-		is_mfm_);
-
 	std::map<int, Storage::Encodings::MFM::Sector> sectors_by_id;
-	for(const auto &sector : sectors) {
-		sectors_by_id.insert(std::make_pair(sector.second.address.sector, std::move(sector.second)));
+	if(density_) {
+		append(parse_track(*track, *density_), sectors_by_id);
+		return;
+	} else {
+		// Just try all three in succession.
+		append(parse_track(*track, Density::Single), sectors_by_id);
+		append(parse_track(*track, Density::Double), sectors_by_id);
+		append(parse_track(*track, Density::High), sectors_by_id);;
+	}
+
+	sectors_by_address_by_track_.emplace(address, std::move(sectors_by_id));
+}
+
+SectorMap Parser::parse_track(const Storage::Disk::Track &track, Density density) {
+	return sectors_from_segment(
+		Storage::Disk::track_serialisation(track, bit_length(density)),
+		density);
+}
+
+void Parser::append(const SectorMap &source, std::map<int, Sector> &destination) {
+	for(const auto &sector : source) {
+		destination.emplace(sector.second.address.sector, std::move(sector.second));
 	}
-	sectors_by_address_by_track_.insert(std::make_pair(address, std::move(sectors_by_id)));
 }
 
-Sector *Parser::get_sector(int head, int track, uint8_t sector) {
-	Disk::Track::Address address(head, Storage::Disk::HeadPosition(track));
-	install_sectors_from_track(address);
+const Sector *Parser::sector(int head, int track, uint8_t sector) {
+	const Disk::Track::Address address(head, Storage::Disk::HeadPosition(track));
+	install_track(address);
 
-	auto sectors = sectors_by_address_by_track_.find(address);
+	const auto sectors = sectors_by_address_by_track_.find(address);
 	if(sectors == sectors_by_address_by_track_.end()) {
 		return nullptr;
 	}
 
-	auto stored_sector = sectors->second.find(sector);
+	const auto stored_sector = sectors->second.find(sector);
 	if(stored_sector == sectors->second.end()) {
 		return nullptr;
 	}
diff --git a/Storage/Disk/Encodings/MFM/Parser.hpp b/Storage/Disk/Encodings/MFM/Parser.hpp
index cdf0dd0345..8bbd912912 100644
--- a/Storage/Disk/Encodings/MFM/Parser.hpp
+++ b/Storage/Disk/Encodings/MFM/Parser.hpp
@@ -9,10 +9,14 @@
 #ifndef Parser_hpp
 #define Parser_hpp
 
+#include "Constants.hpp"
 #include "Sector.hpp"
+#include "SegmentParser.hpp"
 #include "../../Track/Track.hpp"
 #include "../../Drive.hpp"
 
+#include <optional>
+
 namespace Storage::Encodings::MFM {
 
 /*!
@@ -20,7 +24,11 @@ namespace Storage::Encodings::MFM {
 */
 class Parser {
 	public:
-		Parser(bool is_mfm, const std::shared_ptr<Storage::Disk::Disk> &disk);
+		/// Creates a parser that will only attempt to interpret the underlying disk as being of @c density.
+		Parser(Density density, const std::shared_ptr<Storage::Disk::Disk> &disk);
+
+		/// Creates a parser that will automatically try all available FM and MFM densities to try to extract sectors.
+		Parser(const std::shared_ptr<Storage::Disk::Disk> &disk);
 
 		/*!
 			Seeks to the physical track at @c head and @c track. Searches on it for a sector
@@ -28,14 +36,24 @@ class Parser {
 
 			@returns a sector if one was found; @c nullptr otherwise.
 		*/
-		Storage::Encodings::MFM::Sector *get_sector(int head, int track, uint8_t sector);
+		const Storage::Encodings::MFM::Sector *sector(int head, int track, uint8_t sector);
+
+		// TODO: set_sector.
 
 	private:
 		std::shared_ptr<Storage::Disk::Disk> disk_;
-		bool is_mfm_ = true;
-
-		void install_sectors_from_track(const Storage::Disk::Track::Address &address);
-		std::map<Storage::Disk::Track::Address, std::map<int, Storage::Encodings::MFM::Sector>> sectors_by_address_by_track_;
+		std::optional<Density> density_;
+
+		void install_track(const Storage::Disk::Track::Address &address);
+		static SectorMap parse_track(const Storage::Disk::Track &track, Density density);
+		static void append(const SectorMap &source, std::map<int, Sector> &destination);
+
+		// Maps from a track address, i.e. head and position, to a map from
+		// sector IDs to sectors.
+		std::map<
+			Storage::Disk::Track::Address,
+			std::map<int, Storage::Encodings::MFM::Sector>
+		> sectors_by_address_by_track_;
 };
 
 }
diff --git a/Storage/Disk/Encodings/MFM/SegmentParser.cpp b/Storage/Disk/Encodings/MFM/SegmentParser.cpp
index daf64abed9..86a69f0e23 100644
--- a/Storage/Disk/Encodings/MFM/SegmentParser.cpp
+++ b/Storage/Disk/Encodings/MFM/SegmentParser.cpp
@@ -11,10 +11,13 @@
 
 using namespace Storage::Encodings::MFM;
 
-std::map<std::size_t, Storage::Encodings::MFM::Sector> Storage::Encodings::MFM::sectors_from_segment(const Storage::Disk::PCMSegment &&segment, bool is_double_density) {
+std::map<std::size_t, Storage::Encodings::MFM::Sector> Storage::Encodings::MFM::sectors_from_segment(
+	const Storage::Disk::PCMSegment &segment,
+	Density density
+) {
 	std::map<std::size_t, Sector> result;
 	Shifter shifter;
-	shifter.set_is_double_density(is_double_density);
+	shifter.set_is_mfm(is_mfm(density));
 	shifter.set_should_obey_syncs(true);
 
 	std::unique_ptr<Storage::Encodings::MFM::Sector> new_sector;
diff --git a/Storage/Disk/Encodings/MFM/SegmentParser.hpp b/Storage/Disk/Encodings/MFM/SegmentParser.hpp
index 9fc1c8d248..587aa45e4f 100644
--- a/Storage/Disk/Encodings/MFM/SegmentParser.hpp
+++ b/Storage/Disk/Encodings/MFM/SegmentParser.hpp
@@ -9,6 +9,7 @@
 #ifndef SegmentParser_hpp
 #define SegmentParser_hpp
 
+#include "Constants.hpp"
 #include "Sector.hpp"
 #include "../../Track/PCMSegment.hpp"
 #include <map>
@@ -22,7 +23,7 @@ using SectorMap = std::map<std::size_t, Sector>;
 	the segment (counted in bits from the beginning and pointing to the location the disk
 	had reached upon detection of the ID mark) to sector.
 */
-SectorMap sectors_from_segment(const Disk::PCMSegment &&segment, bool is_double_density);
+SectorMap sectors_from_segment(const Disk::PCMSegment &segment, Density density);
 
 }
 
diff --git a/Storage/Disk/Encodings/MFM/Shifter.cpp b/Storage/Disk/Encodings/MFM/Shifter.cpp
index 6790031aa2..ba468c6064 100644
--- a/Storage/Disk/Encodings/MFM/Shifter.cpp
+++ b/Storage/Disk/Encodings/MFM/Shifter.cpp
@@ -16,9 +16,9 @@ using namespace Storage::Encodings::MFM;
 Shifter::Shifter() : owned_crc_generator_(new CRC::CCITT()), crc_generator_(owned_crc_generator_.get()) {}
 Shifter::Shifter(CRC::CCITT *crc_generator) : crc_generator_(crc_generator) {}
 
-void Shifter::set_is_double_density(bool is_double_density) {
-	is_double_density_ = is_double_density;
-	if(!is_double_density) is_awaiting_marker_value_ = false;
+void Shifter::set_is_mfm(bool is_mfm) {
+	is_mfm_ = is_mfm;
+	if(!is_mfm) is_awaiting_marker_value_ = false;
 }
 
 void Shifter::set_should_obey_syncs(bool should_obey_syncs) {
@@ -31,7 +31,7 @@ void Shifter::add_input_bit(int value) {
 
 	token_ = Token::None;
 	if(should_obey_syncs_) {
-		if(!is_double_density_) {
+		if(!is_mfm_) {
 			switch(shift_register_ & 0xffff) {
 				case Storage::Encodings::MFM::FMIndexAddressMark:
 					token_ = Token::Index;
@@ -100,7 +100,7 @@ void Shifter::add_input_bit(int value) {
 		token_ = Token::Byte;
 		bits_since_token_ = 0;
 
-		if(is_awaiting_marker_value_ && is_double_density_) {
+		if(is_awaiting_marker_value_ && is_mfm_) {
 			is_awaiting_marker_value_ = false;
 			switch(get_byte()) {
 				case Storage::Encodings::MFM::IndexAddressByte:
diff --git a/Storage/Disk/Encodings/MFM/Shifter.hpp b/Storage/Disk/Encodings/MFM/Shifter.hpp
index a53689652a..e5db207c1b 100644
--- a/Storage/Disk/Encodings/MFM/Shifter.hpp
+++ b/Storage/Disk/Encodings/MFM/Shifter.hpp
@@ -20,7 +20,7 @@ namespace Storage::Encodings::MFM {
 	a stream of MFM tokens as output. So e.g. it is suitable for use in parsing
 	the output of a PLL windowing of disk events.
 
-	It supports both FM and MFM parsing; see @c set_is_double_density.
+	It supports both FM and MFM parsing; see @c set_is_mfm.
 
 	It will ordinarily honour sync patterns; that should be turned off when within
 	a sector because false syncs can occur. See @c set_should_obey_syncs.
@@ -48,7 +48,7 @@ class Shifter {
 		Shifter();
 		Shifter(CRC::CCITT *crc_generator);
 
-		void set_is_double_density(bool is_double_density);
+		void set_is_mfm(bool is_mfm);
 		void set_should_obey_syncs(bool should_obey_syncs);
 		void add_input_bit(int bit);
 
@@ -72,7 +72,7 @@ class Shifter {
 		Token token_ = None;
 
 		// Input configuration.
-		bool is_double_density_ = false;
+		bool is_mfm_ = false;
 
 		std::unique_ptr<CRC::CCITT> owned_crc_generator_;
 		CRC::CCITT *crc_generator_;
diff --git a/Storage/Disk/Parsers/CPM.cpp b/Storage/Disk/Parsers/CPM.cpp
index 23e5ab3f94..b6a757091b 100644
--- a/Storage/Disk/Parsers/CPM.cpp
+++ b/Storage/Disk/Parsers/CPM.cpp
@@ -16,7 +16,7 @@
 using namespace Storage::Disk::CPM;
 
 std::unique_ptr<Storage::Disk::CPM::Catalogue> Storage::Disk::CPM::GetCatalogue(const std::shared_ptr<Storage::Disk::Disk> &disk, const ParameterBlock &parameters) {
-	Storage::Encodings::MFM::Parser parser(true, disk);
+	Storage::Encodings::MFM::Parser parser(Encodings::MFM::Density::Double, disk);
 
 	// Assemble the actual bytes of the catalogue.
 	std::vector<uint8_t> catalogue;
@@ -29,7 +29,7 @@ std::unique_ptr<Storage::Disk::CPM::Catalogue> Storage::Disk::CPM::GetCatalogue(
 		if(catalogue_allocation_bitmap & 0x8000) {
 			std::size_t size_read = 0;
 			do {
-				Storage::Encodings::MFM::Sector *sector_contents = parser.get_sector(0, uint8_t(track), uint8_t(parameters.first_sector + sector));
+				const Storage::Encodings::MFM::Sector *sector_contents = parser.sector(0, uint8_t(track), uint8_t(parameters.first_sector + sector));
 				if(!sector_contents || sector_contents->samples.empty()) {
 					return nullptr;
 				}
@@ -138,7 +138,7 @@ std::unique_ptr<Storage::Disk::CPM::Catalogue> Storage::Disk::CPM::GetCatalogue(
 				track = first_sector / parameters.sectors_per_track;
 
 				for(int s = 0; s < sectors_per_block && record < number_of_records; s++) {
-					Storage::Encodings::MFM::Sector *sector_contents = parser.get_sector(0, uint8_t(track), uint8_t(parameters.first_sector + sector));
+					const Storage::Encodings::MFM::Sector *sector_contents = parser.sector(0, uint8_t(track), uint8_t(parameters.first_sector + sector));
 					if(!sector_contents || sector_contents->samples.empty()) break;
 					sector++;
 					if(sector == parameters.sectors_per_track) {
diff --git a/Storage/Disk/Parsers/FAT.cpp b/Storage/Disk/Parsers/FAT.cpp
index 528c732485..d534a51395 100644
--- a/Storage/Disk/Parsers/FAT.cpp
+++ b/Storage/Disk/Parsers/FAT.cpp
@@ -77,10 +77,10 @@ FAT::Directory directory_from(const std::vector<uint8_t> &contents) {
 }
 
 std::optional<FAT::Volume> FAT::GetVolume(const std::shared_ptr<Storage::Disk::Disk> &disk) {
-	Storage::Encodings::MFM::Parser parser(true, disk);
+	Storage::Encodings::MFM::Parser parser(Storage::Encodings::MFM::Density::Double, disk);
 
 	// Grab the boot sector; that'll be enough to establish the volume.
-	Storage::Encodings::MFM::Sector *const boot_sector = parser.get_sector(0, 0, 1);
+	const Storage::Encodings::MFM::Sector *const boot_sector = parser.sector(0, 0, 1);
 	if(!boot_sector || boot_sector->samples.empty() || boot_sector->samples[0].size() < 512) {
 		return std::nullopt;
 	}
@@ -108,8 +108,8 @@ std::optional<FAT::Volume> FAT::GetVolume(const std::shared_ptr<Storage::Disk::D
 		const int sector_number = volume.reserved_sectors + c;
 		const auto address = volume.chs_for_sector(sector_number);
 
-		Storage::Encodings::MFM::Sector *const fat_sector =
-			parser.get_sector(address.head, address.cylinder, uint8_t(address.sector));
+		const Storage::Encodings::MFM::Sector *const fat_sector =
+			parser.sector(address.head, address.cylinder, uint8_t(address.sector));
 		if(!fat_sector || fat_sector->samples.empty() || fat_sector->samples[0].size() != volume.bytes_per_sector) {
 			return std::nullopt;
 		}
@@ -130,8 +130,8 @@ std::optional<FAT::Volume> FAT::GetVolume(const std::shared_ptr<Storage::Disk::D
 		const auto sector_number = int(volume.reserved_sectors + c + volume.sectors_per_fat*volume.fat_copies);
 		const auto address = volume.chs_for_sector(sector_number);
 
-		Storage::Encodings::MFM::Sector *const sector =
-			parser.get_sector(address.head, address.cylinder, uint8_t(address.sector));
+		const Storage::Encodings::MFM::Sector *const sector =
+			parser.sector(address.head, address.cylinder, uint8_t(address.sector));
 		if(!sector || sector->samples.empty() || sector->samples[0].size() != volume.bytes_per_sector) {
 			return std::nullopt;
 		}
@@ -143,7 +143,7 @@ std::optional<FAT::Volume> FAT::GetVolume(const std::shared_ptr<Storage::Disk::D
 }
 
 std::optional<std::vector<uint8_t>> FAT::GetFile(const std::shared_ptr<Storage::Disk::Disk> &disk, const Volume &volume, const File &file) {
-	Storage::Encodings::MFM::Parser parser(true, disk);
+	Storage::Encodings::MFM::Parser parser(Storage::Encodings::MFM::Density::Double, disk);
 
 	std::vector<uint8_t> contents;
 
@@ -156,8 +156,8 @@ std::optional<std::vector<uint8_t>> FAT::GetFile(const std::shared_ptr<Storage::
 		for(int c = 0; c < volume.sectors_per_cluster; c++) {
 			const auto address = volume.chs_for_sector(sector + c);
 
-			Storage::Encodings::MFM::Sector *const sector_contents =
-				parser.get_sector(address.head, address.cylinder, uint8_t(address.sector));
+			const Storage::Encodings::MFM::Sector *const sector_contents =
+				parser.sector(address.head, address.cylinder, uint8_t(address.sector));
 			if(!sector_contents || sector_contents->samples.empty() || sector_contents->samples[0].size() != volume.bytes_per_sector) {
 				return std::nullopt;
 			}