All I did was replace the alarm (which took 120V AC directly) with a little AC-DC module (basically what's inside a phone charger) and so it sends out 5V DC when its done cooking. I'm knocking it down to 3.3 and hooking it up directly to the the music box.
music box module available here:
https://www.tindie.com/products/questwise-ventures/canon-in-d-chorus-mechanical-music-box-breakout/