The original play routine for the ST.
AFAIK it doesn't use samples.
It's not a mod, the song-pattern data will be custom.
Original tune that can be played 1:1 on an amiga mod player?
It's not a mod.
The original YM2149 chip can be emulated on the Amiga using MyST plugin for Delitracker/Eagle Player.
Details about using MyST inside another program has been provided to Galahad for 68020+