hey everyone, I didn't see that this had been posted until now—I wrote this as a fun little experiment with audio in the browser. The main hack here was to generate .wav files at the byte level directly in JavaScript by using data URIs. If you want better quality sounds, I suggest using the actual audio APIs that different browsers have exposed. Also, I think the interface came out pretty neat and the CSS for the keys is pretty nice :)

Feel free to ask any questions or suggest any changes. As @danso pointed out, this is the repo https://github.com/mrcoles/javascript-piano