This code is a reverse engineering of the file MODPLAY.BIN, located in the zip file "Asm-Mod" from http://hitmen.c02.at/html/psx_tools.html, that has the CRC32 bb91769f.
The current API behaves roughly the same the original one. The code should provide information about the alterations made to it.
The demo song, "timewarped", written by Jesster, comes from the modarchive with a CC BY-NC-SA 3.0 license, allowing non-commercial adaptations. The file has been converted from MOD to HIT using the MODCONV.EXE software provided by Hitmen.
A modern recreation of the MODCONV.EXE software is available within the PCSX-Redux project itself. See the modconv folder for more information.