How PD is in comparison to cSound and Super Collider?
Both cSound and Supercollider are free too but have no grafical userinterface where you can do your patchwork, they are conducted by textscripts which hold the instrumentdefinitons and score. CSound is the oldest and inherits the traditional software MusicX by Max Mathews. It is the most complete package and offers vast possibilities on almost any platform. Although in former time it was more a soundcompiler it can meanwhile be ran in realtime. Super Collider is more object orientated and newer than cSound but Macintosh only. If cSound is the c language of the dsp ones, Super Collider is C++. Both approaches of user interfaces, grafic and text, got their pros and cons.