MIDI vs MP3: On-Device 125M Piano Models
That MIDI file you’ve been treating like any other audio file? It’s not. It’s a spreadsheet of intentions—a list of who pressed what, when, and how hard—nothing more. No sound, just data. A musician’s left hand finds a chord, the right answers with a melody, but the notes disappear the moment your fingers lift. Unless, of course, the sustain pedal is down. Then those notes linger, ghostly, until you finally release it. That’s the trick MIDI files exploit: they don’t store music, they store the ghost of music, the barely-there sequence of events waiting to be brought back to life. Simon Edwardsson turned that ghost into an autocomplete engine. Almost a year ago he rigged his MIDI piano to an iPhone and taught it to finish his phrases mid-play. Like GitHub Copilot for piano, it watches your hands and suggests where your next note might go. The tool, RollTab, now lives in the App Store for anyone with a MIDI keyboard and an iPad. It’s not magic—it’s a 125-million-parameter model h...