Feature request: make (base) frequency customizable

[Xenwolf]

When I tried to get a listening impression of 11/4, I found that the frequency of the higher tone made this somewhat difficult. In general – at least for my taste – the base frequency could be lowered by an octave. If this wish has chances of being fulfilled, I could imagine that the current frequency as a parameter in the URL would round off this solution nicely.

A possible generalization of this idea would be to let the user specify which of the frequencies to set: the low, high, or middle.

[Xenwolf]

Only now I see that this is not an issue since 11/7 where A = 220hz does the job. It really helps that you made the examples in the about page clickable!

The upper frequency can be specified by using the inverse of the interval, for example 5/6 where A=440Hz.