| Stable release | 5.15 / December 22, 2011 |
|---|---|
| Development status | Active |
| Written in | C |
| Operating system | Cross-platform |
| License | LGPL |
| Website | www.csounds.com |
Csound is a computer programming language for dealing with sound, also known as a sound compiler or an audio programming language, or more precisely, a C-based audio DSL. It is called Csound because it is written in C, as opposed to some of its predecessors. Csound was originally written at MIT by Barry Vercoe, based on his earlier system called Music 11, which in its turn followed the MUSIC-N model initiated by Max Mathews at the Bell Labs. It is free software, available under the LGPL. Its development continued throughout the 1990s and 2000s, led by John ffitch at the University of Bath. The first documented version 5 release is version 5.01 on March 18, 2006. Many developers have contributed to it, most notably Istvan Varga, Gabriel Maldonado (who developed a variant of the system, CsoundAV, which includes image and graphics processing extras), Robin Whittle, Richard Karpen, Michael Gogins, Matt Ingalls, Steven Yi, Richard Boulanger, and Victor Lazzarini.
Developed over many years, it currently has over 1200 unit generators. One of its greatest strengths is that it is completely modular and extensible by the user. Csound is closely related to the underlying language for the Structured Audio extensions to MPEG-4, SAOL.
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Csound takes two specially formatted text files as input. The orchestra describes the nature of the instruments and the score describes notes and other parameters along a timeline. Csound processes the instructions in these files and renders an audio file or real-time audio stream as output.
The orchestra and score files may be unified into a single structured file using markup language tags (a CSD file with filename extension .csd). Here is a very simple example of a unified Csound data file which produces a wave file containing a one second sine wave tone of 1 kHz at a sample rate of 96 kHz:
<CsoundSynthesizer>; <CsOptions> csound -W -d -o tone.wav </CsOptions> <CsInstruments> sr = 96000 ; Sample rate. kr = 9600 ; Control signal rate. ksmps = 10 ; Samples per control signal. nchnls = 1 ; Number of output channels. instr 1 a1 oscil p4, p5, 1 ; Oscillator: p4 and p5 are the arguments from the score, 1 is the table number. out a1 ; Output. endin </CsInstruments> <CsScore> f1 0 8192 10 1 ; Table containing a sine wave. Built-in generator 10 produces a sum of sinusoids, here only one. i1 0 1 20000 1000 ; Play one second of one kHz at amplitude 20000. e </CsScore> </CsoundSynthesizer>
As with many other programming languages, writing long programs in Csound can be eased by using an integrated environment for editing, previewing, testing, and debugging. The one now officially supported is QuteCsound, and it has many features, such as automatic code insertion, integrated documentation browser, integrated widgets for graphically controlling parameters in realtime, plus a button for playing the code.
Version 5.01 was released on March 18, 2006 – 20 years after csound's first release. This latest incarnation of the software is currently available in binary and source code for Linux, Microsoft Windows and Mac OS X from the SourceForge Csound project.[1] It is much improved and expanded compared to the original software, effectively made into a software library with an API. A variety of front ends have been developed for it. In addition to the basic C API, there are also Python, Java, Lisp, Tcl and C++ among other bindings, like one from Haskell which allows control of Csound from a purely functional environment.
The use of plug-ins allows additional capabilities without modifications to the Csound code, as there is the possibility to write user-defined opcodes as extensions to the original language. LADSPA, DSSI, and VST plugins are all supported.
Real-time performance through MIDI has been added in the 1990s, a more recent addition is the support of FLTK widgets (graphical interface components with sliders, knobs, etc.) for controlling real-time audio, and integration of custom graphical interfaces written in Python.
The use of Csound 5 as a live performance tool was enhanced as of October 18, 2011, whereupon Audivation announced Csound For Live,.[1][2] Whilst maintaining the open source nature of Csound, Audivation packaged various opcodes in Max/MSP wrappers suitable for use in Ableton Live, thus integrating realtime performance of multiple Csound patches from within a DAW.
Csound5 was chosen to be the audio/music development system for the OLPC project on the XO-1 Laptop platform.[3]