Signls, a non-linear generative MIDI sequencer for the terminal
Signls is an open-source MIDI sequencer that runs entirely inside a terminal. It is the work of the small emprcl project and is written in Go. The tool describes itself as non-linear and generative: instead of laying events on a fixed timeline, you build a grid of nodes, and signals move across that grid to trigger notes, relay events, or change how the sequence behaves. The result is music that evolves on its own rather than repeating a locked-in pattern.
The grid is the whole interface. Each cell can hold one of nine node types, and each node either emits new signals, relays incoming ones in up to four directions, or triggers MIDI notes. Because signals travel across the grid rather than down a single track, the sequence can branch, split, and fold back on itself. There are nodes named for what they do on the grid: a bang fires, a dice randomizes, a cycle repeats a loop, and a euclid produces Euclidean rhythms from a step count and a pulse count. This is the same family of ideas that Orca, the algorithmic live-coding tool from the Hundred Rabbits collective, made famous a few years ago, and Signls names Orca and the Node-based sequencer Nodal as its direct inspirations.
Signls does not make sound on its own. It is a control surface: it sends MIDI to any connected synthesizer, virtual instrument, or hardware box. Each node can carry note messages — key, velocity, length, probability, channel, and device — plus up to eight control-change messages, which makes it flexible enough to drive parameters on a synth as well as pitch. There is also a randomization layer that can be applied to most parameters, so a single seeded patch can drift into new territory over time. Key and scale transposition work at the grid level, letting a performer shift the whole harmonic context without editing individual nodes.
It is built for live use. Everything is keyboard-driven, with customizable keymaps including QWERTY, AZERTY, and macOS-compatible layouts. The interface supports a bank of 32 saved grids, per-grid MIDI output settings, mute groups, and undo/redo, so a performer can move between scenes and reshape a performance in the moment. Prebuilt binaries are available for Linux, macOS, and Windows, including Raspberry Pi OS on ARM, and it can be installed with a one-line script, Homebrew, or Scoop.
What makes Signls interesting is not any single feature but the design stance underneath it. It refuses the timeline as the default way to think about music, and instead treats sequencing as a spatial, almost physical problem: where do signals go, which nodes do they hit, and what happens when you let chance back in. In that sense it sits squarely in the lineage of algorithmic composition and terminal-based creative tools — software that treats the machine not as a convenience but as an instrument to be shaped. For anyone interested in generative music, live coding culture, or simply tools that reward patience, Signls is worth a look, and it is entirely free and open source.