Csound

Csound is a software system for sound synthesis and signal processing. It provides a programming language and a dedicated engine that can render audio in real time or offline on Windows, macOS, and Linux.

Developed at MIT in the 1980s by Barry Vercoe, Csound grew from the MUSIC-N family into a general-purpose digital signal processing language. It is free and open-source software released under the GNU Lesser General Public License.

Csound uses two text inputs: an orchestra file (.orc) that defines instruments and the opcodes they use, and a score file (.sco) that schedules events to trigger those instruments with specific parameters.

During execution, the engine compiles the orchestra and score, producing audio signals at the target sample rate. It supports both audio-rate and control-rate operation and provides a large library of unit generators (opcodes) for synthesis, sampling, effects, and processing.

Csound can render to a sound file (such as WAV) or provide real-time output through an audio interface, with optional MIDI or OSC input. It supports multimode audio, multiple channels, and various sound-card backends.

The project offers APIs and bindings for several programming languages, including C, C++, Python, and Lua, and GUI front ends such as CsoundQt. Extensive documentation, tutorials, and thousands of example scores accompany the distribution.

Csound is widely used in academic research, education, computer music composition, and media production.