Linux MultiMedia Studio

LMMS (Linux MultiMedia Studio) combines the features of a tracker-sequencer
with powerful synthesizers, samplers, and effects in a modern,
user-friendly graphical interface.
Features include a beat and bassline editor, piano roll, song editor,
built-in synthesizers (ZynAddSubFX, BitInvader, etc.), VST plugin support,
MIDI support, and a large library of samples and presets.