VArranger - vArranger is a PC arranger software, playing Yamaha, Roland and Ketron styles in realtime !
NtEd - Music Score Notation editor.
nimbu - nimbu is the arranger, to play characteristic accompaniments. Accompaniments that allow the title to sound and to be recognized without melody. This arranger performs the way music works. In realtime.
music21 - Music21 is a Python-based toolkit for computer-aided musicology.
JJazzLab - Fed up with boring backing tracks ? Try JJazzLab!
Sibelius - Sibelius is a virtual score creation tool which allows composers to easily create new piano scores, developed by Avid.