introduction on the structure and use of the signal processing softwarePD

PD ("Pure Data") is a realtime signal processing software running under Linux
and Windows.
PD is open source and written in C. It includes a large variety of standart
sound processing routines (e.g. oscillators and filters) and can further be
completed with plugins that are loaded at runtime and may therefore be written
and compiled seperately. Amongst the available extensions, developed by free
programmers, is a library of simple routines for the generation of animated
computer graphics ("gem"). Signal/Control processing modules ("internals" and
"externals") are combined in patches, to execute complex signal processing and
control evaluation "trees". Patches can be build in a simple graphical
environment and can hierarchicaly make use of subpatches.