What about this requires canvas? Seems like it could be done very simply with just divs (and audio elements, of course).

Here is another amusing alternative made using youtube: http://www.youtube.com/watch?v=oD-sSolVDiY

Crashes my Chrome OS (beta channel) browser tab, though when it loaded once there was no sound.

Thank you, I'm using 12.0.742.122 myself but i doubt its chrome rather this thing not being memory profiled at all just yet.

No probs with it on FF Nightly (6.0a1 2011-04-22).

This is cool, but I don't know on what planet "C, Eb, F#" is a major chord. Seems to be off by a half-step (i.e. should be C, E, G)?

Thank you for catching this :) just committed the fix for this.

Yes, the major should be (C E G). (C Eb F#) looks like a C dimnished, though I think it would be better written as (C Eb Gb).

True - for some reason I have this affinity to certain notes being sharp and certain ones being flat (i.e. F# > Gb, but Eb > D#), even though the rule is that it should be consistent based on the key.

An amusing alternative:

http://sweetmusicapp.com

Didn't freeze for my Opera 11.50. Great job, I like musical tools this this a lot!

Completely froze Opera 11.50 for me.