I took a quick look at the Javascript code on saebekassebil's GitHub, and it does seem to be the start of some sort of music theory library. The waveform visualizer demo just doesn't seem to be very revealing of what the library is about.
The actual library does look like it does quite a bit more than waveforms -- it's mostly focused on relationships of notes (in scales, intervals, etc.), and perhaps only secondarily on frequencies. Interesting!
I have done similar work in Java -- built a library exploring note relationships, and also handling basic notation display -- but one of these days I'm going to need to migrate everything from Java applets (I know, I know) to HTML5, so I'm collecting these kinds of resources that may prove useful....
The name selection isn't great, BTW... there's been a well-known music theory website at teoria.com for more than a decade. It's a generic term (just "theory" in Spanish), so this likely isn't a legal issue, but that's going to make it quite hard to find this in Google.
Teoria.js does have a music theory api for working with notes, chords and intervals. I'm actually using it for a site I'm working on: http://groktar.com/?m=kTD4PzaNwv (shameless plug)
