Csound Audio Programming Language

Csound is a free and open-source sound and music computing system originally developed by Barry Vercoe at MIT in 1986 (based on earlier MUSIC-N languages by Max Mathews at Bell Labs, starting with MUSIC I in 1957). Csound is one of the oldest and most widely used software synthesis and audio processing languages, with a rich history spanning over 65 years of continuous development. Key features: two-part language: Csound consists of two text files. The orchestra file (.orc) defines instruments using a C-like syntax with over 1,500 opcodes (operators) for audio synthesis, processing, and analysis. The score file (.sco) defines note events (frequency, duration, amplitude, and other parameters) that trigger instruments at specific times. Unified CSD format: modern Csound uses a single .csd file combining orchestra and score sections, plus options. Synthesis methods: supports virtually every synthesis technique including additive, subtractive, FM (frequency modulation, pioneered by John Channing at Stanford), wavetable, granular, physical modeling (waveguide, modal), and phase vocoder. Processing: over 1,500 opcodes for filtering (lowpass, highpass, bandpass, EQ), delay, reverb (plate, hall, algorithmic), chorus, flanger, distortion, dynamic processing, spectral processing (FFT/IFFT), and spatial audio. Real-time: real-time audio I/O via PortAudio, MIDI input/output, and OSC (Open Sound Control). Plugins: LV2, VST (via CsoundAC), LADSPA, and AU plugin hosting. Frontends: CsoundQt, Cabbage, and Blue provide GUI frontends. CsoundAC for algorithmic composition. Python, Java, C++, C API for embedding. Cross-platform: Linux, macOS, Windows, Android, iOS, WebAssembly. LGPL.