I don't know if this is of any use but a long time ago Amiga & Atari coder Mr.STYCKX (aka Nicolas Pomarede) wrote a YM2149 emulator for the Amiga and his archives include the musics from "Where time Stood Still". He is still active in the Atari scene and co-maintains the Atari emulator Hatari.
The main MyST archive includes the YM2149.bin which works with 68000 and details in the DOC directory of how to use it.
Data Set 4 contains the Fred Gray music to WTSS (YM2149/Misc/YM.WhereTimeStoodStill)
Ok at 20% utilisation of a standard 68k it may be a little slow for use with A500 but still potentially a fun and easy implementation for accelerated Amiga's?