Strawberry Music Player
An open source and free music notation software
The fre:ac audio converter project
Mixxx is Free DJ software that gives you everything you need
SonoBus, a real-time network audio streaming collaboration tool
Audio server, programming language, and IDE for sound synthesis
Audio converter and CD ripper for various formats
A system-wide equalizer for Windows 7 / 8 / 8.1 / 10 / 11
Free open source speech synthesizer for Russian and other languages
An advanced drum machine with pattern-based programming
Audio Tag Editor
Free media player with support for Youtube
Virtual MIDI controller for Linux, Windows and OSX
An Audio/MIDI multi-track sequencer
Graphical editor software for many Boss and Roland effect & synth unit
Multi-Format Audio-Encoder Front-end
wxMP3gain is a free front-end for the MP3gain.
MuldeR's OpenSource Projects
Multiplatform GUI of MP3Gain which adjusts volume of MP3 files
JACK Audio Connection Kit Qt GUI Interface
MIDI libraries for Qt/C++