2026-08-20 / Signal #5
A 125M On-Device Model Now Autocompletes Your Piano Like Copilot
“Copilot, but it finishes the solo you just started.”
The Story
A developer trained a 125M-parameter transformer on cleaned MIDI so it can autocomplete live piano in real time, about 108 notes per second on an iPhone 15. Custom one-note-per-step tokenization, DPO, and aggressive data cleaning made it musical enough to ship as the free RollTab app for MIDI keyboards.
Why It Matters
Local AI is now a jam partner. Art, builders, and the on-device future in one tiny model. Concrete demo, not hype.
Evidence
Builder blog + Show HN (Aug 20) + live iOS app
Sources
Daily scan: 2026-08-20