# Show HN: Duetto – pretrained music transformer that plays a piano with you

> Source: <https://github.com/RiccardoCataldi/duetto>
> Published: 2026-10-24 09:44:20+00:00

## duo-f-blues.mp4

Play a MIDI keyboard and a transformer plays a second piano with you, in real time. It listens like a partner: your key, the chord you play, your pulse, your phrases. It comps while you play and takes the melody when you rest.

The model is the pretrained [Anticipatory Music Transformer](https://github.com/jthickstun/anticipation) (Lakh MIDI), running on a Jetson; the laptop handles MIDI, sound and the piano roll.

## duo-you-comp-it-solos.mp4

Above: you play low chords, the model improvises over them (the **it solos** preset). Files in [samples/duo](https://github.com/RiccardoCataldi/duetto/blob/main/samples/duo).

```
ssh -t jetson sudo jetson_clocks   # after every Jetson reboot
./run_duet.sh                      # on the laptop
```

`run_duet.sh` restarts everything: the model server on the Jetson, the SSH tunnel, FluidSynth, `main.py` on the keyboard and the piano roll. Closing the piano roll stops the duo and saves it in `generated/`.

Without a Jetson: `python -m music_transformer.server` in one terminal, `python main.py` in another (Ctrl+C stops and saves).

## Setup

- **Jetson** (Orin Nano, JetPack 6): the repo in`~/Ai-Duet` with a venv made with`--system-site-packages` (NVIDIA's torch), the model as safetensors in`~/models/music-medium-800k` , power mode MAXN_SUPER, and`ssh jetson` working with a key.
- **Laptop** : FluidSynth with a General MIDI soundfont (`SOUNDFONT=path/to.sf2 ./run_duet.sh` for a sampled grand), and a venv with`pip install mido python-rtmidi pygame imageio-ffmpeg` .
- **Code changes** : the Jetson does not pull from git; copy the files over (`scp music_transformer/*.py jetson:~/Ai-Duet/music_transformer/` ) and run`./run_duet.sh` again. The session tests need torch: run`python -m unittest tests.test_duo_session` there.
- **Logs** :`~/amt_server.log` on the Jetson;`duet.log` ,`fluidsynth.log` ,`pianoroll.log` in`/tmp` on the laptop.

The top of the piano roll says what the model hears (key, chord, tempo) and what it is doing. Keys: F fullscreen, K show or hide the controls, Esc close.

Controls are sliders (drag them; hold Shift to drag finely) and steppers (click the arrows). The wheel or the arrow keys over a control turn it, and the wheel elsewhere scrolls the panel. A double click resets a control, and the bottom of the panel says what the control under the mouse does. A control is dimmed while what it shapes is not happening.

- **AI mind**  - Presets: **duet** ,**call & response** ,**it comps** (it plays the harmony, you improvise),**it solos** (you play the harmony, it improvises),**free**
  - Musical controls: density, harmony, role, dialogue, groove, risk, focus, key follow
  - Range: `lowest` ,`highest` octave
  - Scale: `root` and`scale` force it into a scale (C major, D harmonic minor, F minor pentatonic...) instead of your key
  - Tempo: `bpm` fixes its tempo instead of following yours,`metronome` clicks it
- Presets: 
- **Your sound** ,**AI sound** : instrument, volume, pan, envelope, reverb and delay, in FluidSynth
- **Advanced** : every knob of the model, described in`KNOBS` in[music_transformer/duo.py](https://github.com/RiccardoCataldi/duetto/blob/main/music_transformer/duo.py) , where the defaults are too

Knobs and sound are kept in `~/.config/ai-duet/`.

[PolyForm Noncommercial 1.0.0](https://github.com/RiccardoCataldi/duetto/blob/main/LICENSE): use it, change it and share it freely for anything noncommercial (personal, study, research, education, hobby). Commercial use is not allowed. The model itself is the [Anticipatory Music Transformer](https://github.com/jthickstun/anticipation), under its own license.