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The Csound Manual
(version 3.47)

A Manual for the Audio Processing System 
and Supporting Programs with Tutorials

by Barry Vercoe, Media Lab M.I.T.
and contributors

Edited by Jean Piché, Université de Montréal

 
Copyright 1986, 1997 by the Massachusetts Institute of Technology. All rights reserved. 
Copyright 1997 by Analog Devices Incorporated. All rights reserved.




VERSION

This is the Title Page of the 3.47 html version of the Csound manual. It accompanies the public Csound version 3.47 as compiled by John ffitch of the University of Bath in the UK and available for downloading at : This manual was compiled from the canonical Csound Manual sources kept by Jean Piché and John ffitch. The manual is currently available in html format only. Future releases will also include the following formats: .rtf (Rich Text Format), .txt (ASCII text), and .ps (PostScript format)

The initial sources for this edition of the canonical Csound Manual are based on the work of Peter J. Nix of the University of Leeds, November 1994.

Important Note:

The information contained in this manual is generic. Reference to platform-specific versions of Csound have been removed. Nevertheless, some features described here may not work as indicated on a given platform. When in doubt, please refer to the platform-specific documentation available at the above-mentionned ftp sites.

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Csound Manual Copyright Notice

Copyright 1986, 1992 by the Massachusetts Institute of Technology. All rights reserved.

Developed by Barry L. Vercoe at the Experimental Music Studio, Media Laboratory, M.I.T., Cambridge, Massachusetts, with partial support from the System Development Foundation and from National Science Foundation Grant # IRI-8704665.

Permission to use, copy, or modify these programs and their documentation for educational and research purposes only and without fee is hereby granted, provided that this copyright and permission notice appear on all copies and supporting documentation. For any other uses of this software, in original or modified form, including but not limited to distribution in whole or in part, specific prior permission from M.I.T. must be obtained. M.I.T. makes no representations about the suitability of this software for any purpose. It is provided "as is" without express or implied warranty. Extended Csound developed by Analog Devices, Norwood, MA.

This Hypertext edition of the MIT Csound Manual was prepared for the World Wide Web by Peter J Nix of the Department of Music at the University of Leeds and Jean Piché of the Faculté de musique de l'Université de Montréal. They fully acknowledge the rights of the authors of the original documentation and programs as set out above and further request that this notice appear wherever this material is held and that all hypertext links to it in the accompanying edition of the Manual be retained .


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PREFACE to the Csound Manual

by Barry Vercoe, MIT Media Lab

Realizing music by digital computer involves synthesizing audio signals with discrete points or samples representative of continuous waveforms. There are many ways to do this, each affording a different manner of control. Direct synthesis generates waveforms by sampling a stored function representing a single cycle; additive synthesis generates the many partials of a complex tone, each with its own loudness envelope; subtractive synthesis begins with a complex tone and filters it. Non-linear synthesis uses frequency modulation and waveshaping to give simple signals complex characteristics, while sampling and storage of natural sound allows it to be used at will.

Since comprehensive moment-by-moment specification of sound can be tedious, control is gained in two ways: 1) from the instruments in an orchestra, and 2) from the events within a score. An orchestra is really a computer program that can produce sound, while a score is a body of data which that program can react to. Whether a rise-time characteristic is a fixed constant in an instrument, or a variable of each note in the score, depends on how the user wants to control it.

The instruments in a Csound orchestra are defined in a simple syntax that invokes complex audio processing routines. A score passed to this orchestra contains numerically coded pitch and control information, in standard numeric score format. Although many users are content with this format, higher level score processing languages are often convenient.

The programs making up the Csound system have a long history of development, beginning with the Music 4 program written at Bell Telephone Laboratories in the early 1960's by Max Mathews. That initiated the stored table concept and much of the terminology that has since enabled computer music researchers to communicate. Valuable additions were made at Princeton by the late Godfrey Winham in Music 4B; my own Music 360 (1968) was very indebted to his work. With Music 11 (1973) I took a different tack: the two distinct networks of control and audio signal processing stemmed from my intensive involvement in the preceding years in hardware synthesizer concepts and design. This division has been retained in Csound.

Because it is written entirely in C, Csound is easily installed on any machine running Unix or C. At MIT it runs on VAX/DECstations under Ultrix 4.2, on SUNs under OS 4.1, SGI's under 5.0, on IBM PC's under DOS 6.2 and Windows 3.1, and on the Apple Macintosh under ThinkC 5.0. With this single language for defining the audio signal processing, and portable audio formats like AIFF and WAV, users can move easily from machine to machine.

The 1991 version added phase vocoder, FOF and spectral data types. 1992 saw MIDI converter and control units, enabling Csound to be run from MIDI score-files and external keyboards. In 1994 the sound analysis programs (lpc, pvoc) were integrated into the main load module, enabling all Csound processing to be run from a single executable, and Cscore could pass scores directly to the orchestra for iterative performance. The 1995 release introduced an expanded MIDI set with MIDI-based linseg, butterworth filters, granular synthesis, and an improved spectral-based pitch tracker. Of special importance was the addition of run-time event generating tools (Cscore and MIDI) allowing run-time sensing and response setups that enable interactive composition and experiment. It appeared that realtime software synthesis was now showing some real promise.

PREFACE TO THE EXTENDED OPCODES

During the years 1994-97, Analog Devices Corporation embarked on a major new development in this field. Although the audio, music and multimedia industries had made considerable gain in the previous ten years by embracing digital means of sound synthesis, recording, post production and packaging, the devices that brought about this revolution have remained largely monolithic, single purpose, and inflexible. An up-to-date studio must maintain a large rack of equipment, where each device has a singular function based on application specific technology. The ADI initiative sought to change that by letting programmable devices be truly programmable, and having the audio work done by realtime flexible software. Their strategy began with porting MIT's Csound audio processing software to their SHARC 21060 DSP.

Porting Csound to a floating-point DSP is both enticing and thought-provoking. Being able to run complex Csound instruments in realtime has immediate appeal, and the floating-point intensive Csound software is exceedingly well served by the SHARC hardware and its utilities. The port could have been a simple one. However, a forward-looking audio-processing network is also one that can continually change its profile in response to audio and tactile sensing of human gesture. This naturally invited some major re-thinking.

To support flexible fuctionality and interactivity, Csound was substantially modified by dividing it into two interacting parts:

1) csound - a control or host-resident part for preprocessing the user-defined orchestras and scores, downloading both, creating ftables and sampled data tables, and managing all disk and graphic I/O.

2) dsound - a DSP-resident part for performing sustained hi-fidelity audio processing, with direct on-board audio I/O and MIDI performance sensing.

The two parts are tightly connected by a custom-developed host interface, able to handle simultaneous bi-directional streams of disk-based audio data, control data, score files, MIDI files and graphical data, while the high-fidelity audio processing on the DSP is smoothly maintained.

Given this realtime structure, the signal-processing repertoire of the original Csound was considerably extended and made more effective. Extensions induced by interactive realtime performance enable the system to operate like a modern synthesizer, while those aimed at automatic MIDI file performance enable it to operate as a Karaoke machine. The extensions are most visible in faster generators (loscil1) and better voice input processing (harmon2), along with additional effects processing (chorus, flanging). The new opcodes are identified throughout this manual by an appended asterisk (*). Instruments with these opcodes will run only with the extended hardware. Instruments without them will run in both places.

Although many of the extensions are complex, the added richness has little advantage without realtime live performance, and many of the internal changes were driven by the wish for high- speed response to external keyboards. As a result, most extensions have been written in 21060 assembler language, whose hand coding was found to gain up to 6 times the computational efficiency of its C equivalent. The addition of profiling opcodes (clkon, clkoff) is informative here. From all outward appearances, however, the realtime performable instruments look just like your Csound instruments always did. Your old favorite pieces will still run, but now in realtime, and you can play on top of them too. This is the promise that is being fulfilled.

B.V.


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How to use the Csound Manual

The Csound Manual is arranged as a Reference manual (not a tutorial), since that is the form the user will eventually find most helpful when inventing instruments. Csound can be a demanding experience at first. Hence it is highly advisable to peruse the tutorials included in this document. Once the basic concepts are grasped from the beginning tutorial, the reader might let himself into the remainder of the text by locating the information presented in the Reference entries that follow.

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The Csound Mailing List

A Csound Mailing List exists to discuss Csound. It is run by James Andrews of Exeter University, UK.

To have your name put on the mailing list send a message to:

csound-request@maths.ex.ac.uk

with a single line in the body of the message of the form:

subscribe name@host

Posts sent to csound@maths.ex.ac.uk go to all subscribed members of the list.

 
 
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HTML Csound Manual - © Jean Piché & Peter J. Nix, 1994-97