When the AudioAPI was new in browsers i did something like a virtual kaoss pad in js. With some touchscreen like thing for applying filters (looking and working like the kaoss one) and a sampler with multiple tracks to use and even the possibility to add own sound files into the sampler, recording your work, saving it as wav, ...

Actually sick thing.

But it was quite basic after all. Only two filters, no time correction (the samples got played back as you put them in, so if you are a millisec out of sync - it sounded shit)

Nonetheless I'm very proud of that thing.x)