hrm… maybe my wording wasn’t as clear as I had hoped. It generates the audio ahead of time (as base64 dataURI wave files)—the on-the-fly part is that it’s generated in JavaScript each time you make changes to the settings, like wave-form and volume response (click on the square in the top right or type "?" to see changeable options).

I assume the audio APIs would make less click-y sounds (and don't suggest manually created wave files as a solid way to create perfect sounds), but I also sort of like the clicks. When I presented this at Hack and Tell NYC, I claimed that you had to play it in Firefox 12 to get hear the exact clicks that were originally intended in the product ;?j