You can change between drums or a synth sound (also using the D or S keys). The URL also holds the state, so you can send it to a pal to have them listen to your masterpiece. If you hit a bug, refreshing usually makes it go away.
The Improvise button will auto generate drums to match your synth using ~*machine learning*~ via Magenta.js and a recurrent neural network. In the browser!!
Ok, go make fun things now and tell me about it!