/ In the lab
Next: the instrument you already own
Not everything has a cable. So we're teaching the browser to listen — pitch, attack, pulse, tone, loudness, pulled out of the microphone about twenty times a second and turned into something a game can read.
You play a few seconds of what "go fast" sounds like, and a few of what "stop" sounds like, and after that your own trumpet, snare or guitar is the gamepad. No adapter, no pickup, no special instrument.