Sibelius - Sibelius is a virtual score creation tool which allows composers to easily create new piano scores, developed by Avid.
Guitarix - Guitarix is a simple Linux Rock Guitar Amplifier for https://alternativeto.
MMA - “MMA—Musical MIDI Accompaniment” is an accompaniment generator.
GNUitar - GNUitar is guitar effects software that allows you to use your PC as guitar processor.
Sundog Scale Studio - The MIDI chords and melodies laboratory
Ampire - State Space Modeled guitar amp/cab/stompbox simulator.