Sonic Pi: concurrent live_loops and sync

A real Sonic Pi set — the kind you’d play at an algorave or stream from a bedroom rig — is never one loop. It is a drum part, a bassline, and a melodic layer running at once, staying locked to a shared groove while you rewrite the music underneath the audience’s feet. This module builds exactly that skill: keeping three concurrent voices in phase and restructuring the piece live, with the audio never stopping.

The arc starts from the beginner’s wall: writing two infinite loops in sequence and hearing only the first. Understanding why sequential loops fail motivates everything after. From there, a first supported exercise layers parts with “in_thread do … end launches a concurrent execution path” and discovers the Run-button mechanic — each press adds a thread rather than restarting. That immediately exposes the duplicate-instance trap, solved by named threads, which are also the conceptual bridge to live_loop’s hot-swap behaviour. A second exercise deliberately lets two loops drift, then repairs them using “cue broadcasts a named event and sync blocks until the next occurrence” and the auto-generated cue events every live_loop emits. Time State (get/set) then replaces fragile shared variables so loops can coordinate deterministically. Finally, the define/redefine pattern — swap a function’s body while a loop keeps calling it — gives you live restructuring.

The required atoms gate the capstone directly: you cannot run three loops, phase-align them, or hot-swap a function without them, and the drills (cue/sync, loop-to-loop sync, redefine-while-running) must be automatic under performance pressure. Supporting atoms enrich the same territory — the race-condition misconception explains why Time State exists, Reich-style phasing turns drift into an aesthetic, control of SynthNode references enables post-trigger parameter gestures, and the MIDI/OSC atoms extend sync to external hardware for a bigger rig.

Runnable examples

Generated from the context/ instrument corpus by concept (redistributable idioms only). Do not edit — regenerate with gen-module-examples.mjs.

live-hot-swap

live_loop :x do; play 60; sleep 1; end

_{sonicpi-0048 · CC0}

Ndef(\a, { SinOsc.ar(220) * 0.1 }).play

_{supercollider-0037 · CC0}

event-driven-sync

live_loop :hats, sync: :tick do; sample :drum_cymbal_closed; sleep 0.25; end

_{sonicpi-0049 · CC0}

Event e; fun void hit(){ e => now; <<<"go">>>; }
spork ~ hit(); spork ~ hit(); 1::ms => now; e.broadcast();

_{chuck-0014 · MIT}