Scheme Note is a Scheme-like music file format and MIDI conversion tool. It takes a text file, which is a representation of a song, loosely tied to a MIDI-like event structure, and outputs a corresponding MIDI file. It is hand-editable for simple songs, and should be very easy to parse for a GUI.
Rumor is a realtime monophonic (with chords) MIDI keyboard to Lilypond converter. It receives MIDI events, quantizes them according to its metronome on the fly, and outputs intelligently handwritten-like corresponding Lilypond notation. Tempo, meter, key and other parameters can be set via commandline options. Rumor can use ALSA/OSS or emulate MIDI input with computer keyboard. It is scriptable with Guile. It has been tested on several major J. S. Bach organ pieces (see links to Mutopia in the documentation).
FrAid (Fr[actal] Aid) is a programming language that is appropriate for mathematical computations, visualization, batch processing, and more. It features both a standalone application that provides a programming environment for the language and a system for integrating the language with Java. The Java interface allows mathematical equations and formulas to be used with Java code, making it easier to process numerical computations, symbolic computations, imaging, CAD, and more.