MidiAndMusicXmlPlayer plays Midi-files and MusicXML files. These are note files made by some Notation Program. See https://www.programfabriken.com to see a picture of the main window (classical Delphi look)
The voices/instruments of a tune may be selected by checkmarks. The tempo and transposition may be changed. Also the voices/instruments may be changed (to a few other instruments). E.g. I normally select the bas-voice and remove the checkmark for sopran, alt, tenor, then I try to learn the bas-voice and maybe a little slow. When I think I can sing the bas-voice I put on the other voices and may even remove the bas-voice to check that I can sing it alone.
The panorama (move instrument from left to right) can be set. All this in order to better hear the single voices/instruments. Intended use is learning a tune, that you want to sing or play.
The compiled program can be downloaded from: https://www.programfabriken.com/MidiAndMusicXmlPlayerPc64.zip
Some MusicXML-test files can be found at: https://wpmedia.musicxml.com/wp-content/uploads/2017/12/xmlsamples.zip
Quartertones and Microtones are also played as in Air a la Grecque of Charles de Lusse: https://programfabriken.com/Air_a_la_Grecque.zip
and in the Turkish Makam-music. See: "Karaosmanoglu, M. K. (2012). A Turkish makam music symbolic database for music information retrieval: SymbTr. Proc. Int. Society for Music Information Retrieval (ISMIR).
To get better sounds you can install another Synthesizer (instead of the poor quality Windows-soundfont). The soundfont called "Fluid" is good.
About the MAC-OS-version see https://www.programfabriken.com (Source - load the program from Appstore)
A draft manual exits on: https://programfabriken.com/MidiAndMusicXmlPlayerManual.odt