Csound

A “domain-specific computer programming language for audio programming” — and a sound synthesis system, which is the same statement twice. Barry Vercoe wrote it at the MIT Media Lab in 1985 out of his earlier Music 11, in the MUSIC-N line Max Mathews started at Bell Labs. John Fitch led development at the University of Bath through the 1990s and 2000s. Around 1,700 unit generators (“opcodes”) now. Written in C, LGPL 2.1+, on Linux, Windows and macOS; 6.18.1 in November 2022, with Csound 6 having added live coding — recompiling an orchestra while it plays.

T2 — third-party encyclopaedic.

The orchestra and the score

Csound splits a piece in two. The orchestra defines instruments: what generates and processes sound. The score lists notes and parameters over time. A .csd file can hold both behind markup tags. That is the oldest signal-routing model this wiki has, and it is worth setting against vcv-rack and the Eurorack lineage: same idea — build a signal path out of small units and then drive it — with the patch written as text rather than made of cables, and the performance written as data rather than played.

It also predates everything else in the corpus by decades and generalizes it. fm-synthesis, additive-synthesis and granular-synthesis are each a fixed engine in the instruments this wiki usually covers; in Csound they are just opcodes you wire up, so the method is not the product’s identity. The nearest thing here to a synth that has no sound of its own.

Rendering versus real time

Csound will render to a file or synthesize live, and the historical order matters: the MUSIC-N family began when audio synthesis was slower than real time and a piece was computed, not played. Live coding arriving only at version 6 marks how long that assumption held. The analog-vs-digital argument in this wiki is usually about the character of a circuit; Csound is the reminder that early digital synthesis had a plainer disadvantage, which was that you could not hear it yet.

Cross-spoke

This is also a programming language, and ../programming-languages-wiki holds the language-design corner of the hub (it took twelve language sources on 2026-08-06). The routing call: Csound’s substance here is sound synthesis, so the page lives in music-tech-wiki and the language angle — a DSL whose two file types encode “instrument” and “performance” as separate program parts — is noted there as adjacency.

Related

vcv-rack · fm-synthesis · additive-synthesis · granular-synthesis · analog-vs-digital · synthesizer · synthesis