Nyyrikki just sent us a PT3 Player for MSX-DOS. This tool can be used to play PT3 files created with Vortex Tracker II on PSG from an MSX-DOS commandline. Two weeks ago, Alfonso D.C. released the ASM code to the PT3 player, making it possible to use PT3 music in MSX productions, such as Muzix.
Apart from these releases, Maggoo and Guillian also released PT3 players, mentioning them in this forum thread. You can find Maggoo's quick and dirty PT3 loader for MSX-dos right here, while Guillian has created a PT3 player for DOS and a PSG demo in ROM format.
Relevant link: PT3 Player for MSX-DOS