Calliope is a mature music score notation editor written by Professor William Clocksin in 1993 that originally ran on NeXTStep machines and has since been ported to OpenStep systems such as Windows and Rhapsody (using the Yellow Box API). It is currently in the process of porting to MacOS X using the Cocoa API and subsequently Linux using GnuStep. It is written in Objective C and links against the open source MusicKit/SndKit API also hosted on GitHub.com. Calliope offers good support for typesetting modern and early musical scores, including lyrics and lute tablature. Making the source code open is intended to complete the porting and modernise the file format support as well as for incorporating users bug reports and fixes.