rsll is a live MIDI looper with a terminal UI, written in Rust. It connects to your MIDI controller over JACK, records what you play into looping tracks, and plays everything back through a software synth such as FluidSynth or sfizz. Everything is driven from the controller itself — arm a track, punch in, layer loops, switch scenes — so you can keep your hands on the keys while the TUI gives you live feedback on tracks, recording state, and the master clock.
- 🔁 Multi-track looping — record and overdub up to 8 independent tracks, each with its own MIDI channel, program (instrument), volume, and loop length
- 🥁 Drum pads — pad bindings mapped to drum notes on channel 10, with per-scene kits and velocity scaling
- 🎬 Scenes — multiple song setups in
scenes/*.toml(BPM, time signature, track programs, drum kits); switch between them live from the controller - ⏱️ Master clock & metronome — configurable BPM, PPQN, and time signature, with a toggleable metronome (downbeat + subdivision clicks)
- 🎯 Quantize — optional snapping of recorded notes to the nearest sixteenth
- ↩️ Undo / clear — per-track undo history, clear-track, and clear-all controls
- 🔇 Track mute and per-track volume via a mapped knob
- 💡 LED feedback — pad LEDs reflect track state (on / off / blinking while armed)
- ⏲️ Arm time — configurable minimum delay between arming record and punch-in
- 🔄 Live config reload —
hardware.tomland scene files are watched and reloaded while running, no restart needed - 💾 MIDI export — press
sin the TUI to export your loops to a standard MIDI file
- A Linux system with JACK (rsll uses
midirwith the JACK backend) - A MIDI controller (the default
hardware.tomlis set up for an Akai MPK mini IV — adjust the port patterns and key bindings for your hardware) - A synth to make sound: FluidSynth or sfizz must be running so rsll has an output port to connect to
cargo build --releaseThe binary lands at target/release/rsll.
-
Start your synth first, e.g. FluidSynth with a General MIDI soundfont:
fluidsynth -a jack -m jack /path/to/GeneralUser.sf2
(or launch sfizz instead)
-
Plug in your MIDI controller.
-
Launch rsll from the project directory:
./target/release/rsll
rsll will scan for MIDI ports matching the regex patterns in hardware.toml, connect inputs/outputs automatically (and keep retrying if a device appears later), load every scene from scenes/, and start the TUI.
| Flag | Description |
|---|---|
-s <scene.toml> |
Load a single scene file instead of the scenes/ directory |
-c <hardware.toml> |
Use an alternate hardware config file |
-h, --help |
Show usage |
| Key | Action |
|---|---|
q |
Quit |
s |
Export loops to a MIDI file |
hardware.toml— MIDI port regex patterns, controller key bindings (record, clear, undo, mute, quantize, track pads, drum pads, scene up/down, BPM/volume knobs), LED channels, and record arm time. Live-reloaded while running.scenes/*.toml— one file per scene: BPM, metronome default, time signature, PPQN, per-track channel/length/program, and the drum kit (notes, channel, velocity multiplier). Looplengthaccepts either a raw tick count (length = 96) or a musical fraction string relative to a whole note (length = "1/8",length = "1/12"); at PPQN 24 a whole note is 96 ticks, so"1/1"= 96,"1/4"= 24,"1/8"= 12.gm.toml— General MIDI program number → instrument name table used for display.