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Pd (aka Pure Data) is a real-time graphical programming environment for audio, video, and graphical processing. It is the third major branch of the family of patcher programming languages known as Max (Max/FTS, ISPW Max, Max/MSP, jMax, etc.) originally developed by Miller Puckette and company at IRCAM. The core of Pd is written and maintained by Miller Puckette and includes the work of many developers, making the whole package very much a community effort.

NodeBox is a new software application for creating generative art using procedural graphics and a new way to approach graphic design.

vvvv is a graphical programming environment for easy prototyping and development. It is designed to facilitate the handling of large media environments with physical interfaces, real-time motion graphics, audio and video that can interact with many users simultaneously.

Context Free is a program that generates images from written instructions called a grammar. The program follows the instructions in a few seconds to create images that can contain millions of shapes.

Csound is a sound design, music synthesis and signal processing system, providing facilities for composition and performance over a wide range of platforms. It is not restricted to any style of music, having been used for many years in the creation of classical, pop, techno, ambient, experimental, and (of course) computer music, as well as music for film and television.

Prismacode is an easy programming language for creating 2D geometric graphics. It's a combination of logic and art -- there are no right or wrong answers.

Evaldraw allows you quickly write small programs in its C-like language. It supports static variables, enums, arrays, functions and just recently structs.