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The CREATE Signal Library (CSL) Project Home Page

What is CSL?

The CREATE Signal Library (CSL, pron. "sizzle") is a cross-platform (Mac, Linux, MS-Windows, iOS, Android, etc.) software framework for sound synthesis and digital audio signal processing. It is implemented as a C++ class library to be used as a stand-alone synthesis server, or embedded as a library into other programs. 

CSL is frequently used together with JUCE, a comprehensive C++ class library for multimedia and GUI programming, but it can also be used for stand-alone apps without JUCE, or with other GUI frameworks such as Qt.

This page describes CSL in more detail, gives examples of its usage, and provides instructions on how to download it.

NewsCSL demo GUI

CSL 6.0 Released on github

To coincide with the release of JUCE 6.0, CSL 6.0 is now available at its new home on github.
To download the full source tree, go to,

and either grab the zipped archive file set or use the shell command,

git clone

As always, RTFM; there is a folder of papers and a complete doxygen cross-reference.

Watch "The CSL Show" Screencasts

Show 1: A Tour of CSL (22 min)

Show 2: CSL Internals (4:20 min)

Show 3: NEW DEMO (May, 2020) CSL + Siren Integrated (32 min)

For discussion, we use the JUCE forum; please see

Older News

CSL 5.2 Available (stale)

CSL 5.2 is now available as a zip archive at the link

or other SVN client to get the CSL code tree. CSL 5.2 has been tested on Mac OSX (10.6 and higher), MS-Windows 7, Ubuntu Linux 11.10, and iOS 5 and newer (Android support expected soon).

This release adds support for newer JUCE releases (i.e., it doesn't require a patched JUCE library as before), but it requires LibSndFile ( for sound file I/O (which isn't needed by all applications anyway). This version also uses the IntroJucer app to generate build projects or Makefiles, so users are expected to be able to build and use the JUCE tools. To use this, look in the CSL_JUCE folder in the distribution.

The main addition is support for MP4 and FAAD files via the libMAD and libFAAD libraries (not included in the simplest JUCE build). There are also a whole raft of fixes and tune-ups...

Download Links

CSL 5.1 now also on Linux The SVN repository now has working projects for Mac OSX 10.6, MS-Windows XP/Vista, and Ubuntu Linux.

System Requirements

CSL 5.0g now on MS-Windows

We have a new VisualStudio project for CSL 5.0 that uses JUCE 1.50 to build on MS-Windows XP and Vista. It requires that JUCE and the DirectX9 SDKs be installed. Here's a screen shot of the CSL_JUCE 5.0 demo running (with audio) on XP.

CSL Subversion Repository Available (it's no longer there; see the github links above.)CSL demo GUI

To access the CSL subversion (svn) code repository at the Media Arts & Technology (MAT) servers at the University of California, Santa Barbara (UCSB), use any SVN client or shell terminal and enter the command,

svn co

to down-load the latest CSL source, doc, and Mac/Linux/Windows build projects to your machine.

You can also browse the whole file tree on-line as,

See, e.g.,

The CREATE Signal Library (CSL) CSL classes

The CREATE Signal Library (CSL, pron. "sizzle") is a cross-platform general-purpose software framework for sound synthesis and digital audio signal processing. It is implemented as a C++ class library to be used as a stand-alone synthesis server, or embedded as a library into other programs.

CSL provides simple and reusable implementations of all common sound synthesis and processing techniques, and includes support for a wide variety of audio I/O interfaces such as PortAudio, RTAudio, JACK, VST, CoreAudio and JUCE. As illistrated in the screen shots below, we generally use JUCE for graphical user interfaces to CSL programs.

In previous versions, it was complicated to install CSL because it used a variety of 3rd-party APIs for sound playback (e.g., PortAudio), sound file I/O (e.g., libSndFile), FFT (e.g., FFTW), and GUI-building (e.g., Qt). As of CSL 5.0, we have based the system on JUCE (Jules' Utility Class Extensions, see here); this means that frameworks for real-time sound I/O, sound file I/O, and GUI construction are the same. Note that we use an extended version of JUCE 1.50; see the download links below for our enhancements.

CSL Downloads


Related Packages

CSL Granulator Project Description 


The CREATE Signal Library (CSL) is a flexible, portable, and scalable C++ software framework for sound synthesis and digital signal processing. The following sections describe the basic system requirements and present the current design and its implementation, giving extensive code examples along the way. The initial design of CSL dates back to 1998, but the  version 4 implementation was undertaken by students in the MAT 240D Sound Synthesis Techniques course at UCSB in the Spring of 2006. A simple C++ implementation of a sound synthesis framework (in less than 1000 lines) was introduced at the start of the class, and during the quarter the students added a large number of synthesis classes (refining the basic framework significantly as they went). CSL is now an open source project; the current source code and documentation can be retrieved over the Internet from

What CSL is

CSL is a simple yet powerful library of sound synthesis and signal processing functions. It is packaged as an object-oriented class hierarchy for standard DSP and computer music techniques, and is suitable for integration into existing applications, or use as a stand-alone synthesis/processing server. CSL is similar to the JSyn (Burke), CommonLispMusic (Schottstaedt), STK (Cook), and Cmix (Lansky) frameworks in that it is integrated as a library into a general-purpose programming language, rather than being a separate “sound compiler” as in the Music-N family of languages (CMJ tutorial on sound compilers). CSL is designed from the ground up to be used in distributed systems, with several CSL programs running as servers on a local-area network. These CSL DSP servers receive control commands via the network and send their output sample blocks to other servers over the network.

CSL supports the following synthesis/interaction techniquesCSLL Spectrogram

What CSL is not

CSL is not a music-specific programming language such as Music-N or SuperCollider (McCartney); rather, CSL programs (i.e., CSL-based servers) are written in C++ and compiled with the CSL library. CSL has no graphical user interface (as in Max [Puckette] or Kyma [Scaletti]), but it is expected that GUIs will be built that manipulate “patches” and “scores” for CSL. CSL is not a music representation language such as Smoke (Pope), rather it is a low-level synthesis and processing engine. CSL has no scheduler, it simply responds to in-coming control messages (received, e.g., via MIDI or OSC) as fast as it can.
This flexibility means, however, that CSL can serve a number of different purposes, from being used as a plug-in library for other applications to serving as the basis of synthesis servers for other front-end languages, such as MPEG4/SAOL.


In the most recent version, CSL has been simplified to use the sound and sound file I/O facilities of JUCE (Jules' Utility Class Extensions). This means that fewer out-board libraries and APIs need to be installed to start using CSL. Users can still use other sound IO APIs (e.g., portAudio, RTAudio or platform-native APIs) or sound-file APIs (e.g., libSoundFile), but the JUCE-only version is simpler to install and get running. The only 3rd-party library needed for the CSL core is JUCE.

The CSL Core

oscillator classses

In contrast to the traditional MusicN stand-alone sound compiler, CSL is packaged as a class library in a general-purpose programming language (C++). The simplest CSL program is a 5-line main() function in a simple C program, and it is intended that CSL can be used in several ways, including for the development of stand-alone interactive (MIDIor OSC-driven) sound synthesis programs, serving as a plugin library for other applications or plug-in hosts, or as a back-end DSP library for programs written in scripting languages. CSL is designed from the ground up to be used in distributed systems, where networks of CSL programs run as servers on a local-area network, streaming control commands (MIDI and OSC) and sample buffers (RTP) between them.

CSL Example

    // This is a simple 2-envelope FM program -- paste this into a main() function

    float frq = 440.0f;                  // float values for freq and dur
    float dur = 0.25f;

    IO theIO;                            // create an IO object
    Sine car, mod(frq);                  // create 2 oscillators: carrier and modulator
                                         // amplitude env = std ADSR
    ADSR a_env(dur, 0.1, 0.1, (dur - 0.6), 1); 
                                         // index env = time/value breakpoints
    Envelope i_env(dur, 0, 0, 0.1, 2, 0.2, 1, 2.2, 8, dur, 0);

    a_env.setScale(0.2);                 // make ampl envelope quieter
    i_env.setScale(frq * 3.0f);          // multiply index envelope by mod freq * 3 (index depth)

    mod.setScale(i_env);                 // scale the modulator by its envelope
    mod.setOffset(frq);                  // add in the base freq

    car.setFrequency(mod);               // set the carrier's frequency
    car.setScale(a_env);                 // scale the carrier's output by the amplitude envelope

    logMsg("CSL playing FM...");         // print a message and play
    theIO.setRoot(car);                  // set the IO's root to be the FM carrier;                        // open the IO
    theIO.start();                       // start the driver callbacks and it plays!

    a_env.trigger();                     // reset the envelopes to time 0

    sleepSec(dur + 0.25);                // sleep for dur plus a bit

    logMsg("CSL done.");
    theIO.stop();                        // stop the driver and close down

Getting started using CSL

We assume CSL users are proficient C++ programmers and know the native development environment of their platform.

Down-load and unpack JUCE V 1.50 and compile its base library.

Down-load and unpack CSL 5.0 and read the documentation. CSL assumes it's installed in the folder ~/Code/CSL; there are some default settings in CSL/Kernel/CSL_Types.h that have to be changed if you put it somewhere else. The system assumes JUCE is in ~/Code/juce (../juce from the root of the CSL hierarchy).

The best way to get started is to look at the Doxygen-generated API documentation in

You can untar this file to get the full HTML doc and to print out and study the files
    CSL/Kernel/CSL_Types.h    (note the system defaults here)
    CSL/Kernel/CSL_Core.h      (the kernel classes are here)
    CSL/Sources/SimpleSines.{h,cpp}    (this is a tutorial for writing unit generators)

To compile the sources, you may need to create the links in the CSL/Includes folder; to do this, open a UNIX shell (AKA terminal) and execute the commands,
        ### change to the Includes folder
    cd CSL/CSL/Includes

        ### make symbolic links from the include files to this folder
    ln -s ../*/*.h .
    ln -s ../Spatializers/*/*.h .

Now, you should be able to use the Mac XCode project in JUCE, the premake script and makefile in Linux, or to build an Eclipse project on Windows. The supplied VisualStudio projects are known to produce errors because of CSL's non-Windows-compatible header and code.

Once you have the development environment set up, build the JUCE demo GUI (shown in the figures above). This app has 2 menus at the bottom of the pane to select a test suite and a specific test, and a play/stop button next to these menus. The source code for the tests is in the folder CSL/Tests; the list of tests is included below.

CSL Demo GUI Menu

The source code for all these tests is in the CSL/Tests directory (and file group in the IDE); it's a good way to learn CSL to run the JUCE demo in an XCode/Eclipse debugger and set breakpoints in the test functions while using the GUI.

For more information, please join the discussion on the JUCE forum or contact Stephen Pope [stephen (at) FASTLabInc (dot) com].