Yoshimi is a software audio synthesizer, originally forked from ZynAddSubFX.
LMMS
Let’s make music
with a free, cross-platform tool for your computer.
drumkv1
drumkv1 is an old-school all-digital drum-kit sampler synthesizer with stereo fx.
Patroneo
An easy to use, pattern based midi sequencer, a program that sends digital “notes” to software instruments such as synthesizers and samplers.
ΜΗ
Non is the result of one man’s desire to build a complete free-software Digital Audio Workstation on GNU/Linux that really works–on accessible hardware.
Rosegarden
Rosegarden is a music composition and editing environment based around a MIDI sequencer that features a rich understanding of music notation and includes basic support for digital audio.
Luppp
Luppp is a music creation tool, intended for live use. The focus is on real time processing and a fast and intuitive workflow.
padthv1
padthv1 is an old-school polyphonic additive synthesizer with stereo fx.
Cecilia
Cecilia is an audio signal processing environment aimed at sound designers. Cecilia mangles sound in ways unheard of. Cecilia lets you create your own GUI using a simple syntax. Cecilia comes with many original built-in modules and presets for sound effects and synthesis.