Cecilia is an audio signal processing environment using Csound as its audio engine. Cecilia lets you create your own GUI (grapher, sliders, toggles, popup menus) using a simple syntax. Cecilia comes with many original builtin modules for sound effects and synthesis. Previously written in tcl/tk, Cecilia was entirely rewritten in Python/wxPython and uses the Csound API for communicating between the interface and the audio engine.

Cecilia was designed by and for musicians and sound designers. First and foremost, we wanted to make the most powerful and open-ended sound processing language readily usable for composers, researchers and sound artists. Creators will find in Cecilia all the tools necessary to make sound what they want it to be. Included are all the traditional sound processing devices such as EQs, compressors and delays adapted for the most simple applications and the wildest imaginable sonic contortions.

If you are an advanced Csound user you may think that FLTK widgets have now made Cecilia redundant. This is not the case, as it is much faster to build an interface with Cecilia, and there are many features not yet covered by the FLTK opcodes, like logarithmic faders and curves. The downside for the advanced user is that the new opcodes are not yet inculded in the built-in reference. New opcodes are none the less perfectly functionnal in Cecilia, as Cecilia is merely an interface to Csound.

Cecilia is written in Tcl/Tk so as to be portable. So far, Cecilia has been released for Windows, Linux, IRIX, MacOS X, and MacOS. The IRIX and MacOS ports are currently not maintained but newer versions might just work on these platforms. Cecilia is released under the terms of the GNU General Public Licence.

Cecilia was initially developed by Alexandre Burton and Jean Piché of the Faculté de Musique at Université de Montréal from 1995 to 1998. It was then ported to Linux by Dave Philips. Stephan Bourgeois and Yves de Champlain also contributed. It is currently maintained by Bill Beck, Phil Sobolik, and Hans-Christoph Steiner.