The abc4j java library provides API to handle abc musical notation using java (>=jdk 1.2 but core classes only rely on 1.1.8).
It provides a parser to parse tunes written in abc notation, and other classes in order to support midi playback, music score display etc etc. It only supports abc v1.6 (for now... :). You can extend the basic capabilities of the library to implement your own dedicated features like improved midi player, or whatever...
The library also comes with the "ABCynth" Java Application that demonstrates some of the features of the library.
For further information, please have a look at the tutorials http://code.google.com/p/abc4j/w/list or download the latest javadoc http://abc4j.googlecode.com/files/abc4jApiDoc_v0.5.zip
You can also have a look at the demo applets to get an idea of what can be achieved with abc4j :
Any idea, improvement, request or simply curious about how it works ? use the discussion group at http://groups.google.com/group/abc4j
Coming soon :
Music model : Ties and slurs, Lyrics, abc eXtended commands. Score Display : Chords, Up-bow and down-bow (already included in the music model), Lyrics display. Export : MusicXML (very first version in 0.5)