This is PMX, version 2.6.18. PMX provides a preprocessor for MusiXTeX.

pmxab builds a TeX input file based on a .pmx input file in a much
simpler language, making most of the layout decisions by itself. It has
most of MusiXTeX's functionality, but it also permits in-line TeX to
give access to virtually all of MusiXTeX. For proof-listening, pmxab will
make a MIDI file of your score.

scor2prt is an auxiliary program that makes parts from a score.

The author of pmxab and scor2prt is Don Simons (dsimons@roadrunner.com).