Guitarix - Guitarix is a simple Linux Rock Guitar Amplifier for https://alternativeto.
NtEd - Music Score Notation editor.
TH-U - World class guitar amps and effects for PC and Mac
Sibelius - Sibelius is a virtual score creation tool which allows composers to easily create new piano scores, developed by Avid.
Ampire - State Space Modeled guitar amp/cab/stompbox simulator.
music21 - Music21 is a Python-based toolkit for computer-aided musicology.