Qtractor - An Audio/MIDI multi-track sequencer
http://qtractor.sourceforge.net/
http://sourceforge.net/projects/qtractor/
Qt 4 - C++ class library and tools for cross-platform development and internationalization
JACK Audio Connection Kit
ALSA - Advanced Linux Sound Architecture
libsndfile - C library for reading and writing files containing sampled sound
http://www.mega-nerd.com/libsndfile/
libvorbis - Ogg Vorbis audio compression
libmad - High-quality MPEG audio decoder
http://www.underbit.com/products/mad/
libsamplerate - The secret rabbit code, C library for audio sample rate conversion
LADSPA - Linux Audio Developer’s Simple Plugin API
QjackCtl - JACK Audio Connection Kit - Qt GUI Interface
http://qjackctl.sourceforge.net/
http://sourceforge.net/projects/qjackctl/
Cakewalk - Powerful and easy to use products for music creation and recording
ftp://ftp.cakewalk.com/pub/InstrumentDefinitions/
SoundTouch - Sound Processing Library
http://www.surina.net/soundtouch/
rncbc.org - The personal web presence of Rui Nuno Capela, creator and developer of Qtractor and other applications or application GUIs such as QjackCtl (a GUI for jackd), Qsynth (a GUI for fluidsynth), Qsampler, etc.