This is PMX, version 2.94 (2020-03-18). 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.

PMX may be freely copied, duplicated and used in conformance
to the GNU General Public License (Version 3, 29 June, 2007,
see included file gpl.txt).

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