It's very clever, but it's not very sophisticated; it's just data: URLs of the samples. Beatboxes are a kids project on Scratch; I'm surprised it took so long to get a good one in Javascript. =)
When someone gets the WAV/PCM decode and signal processing stuff written up in JS, then we'll have proved something.
I have found that the most worthwhile projects take simple data and applies it in unique and useful ways. It's so difficult to get to interesting/relevant data much of the time. Algorithmic complexity is great, but for my part, I just want to make something good. This thing is fun, and that's pretty good.
When someone gets the WAV/PCM decode and signal processing stuff written up in JS, then we'll have proved something.