the hardware that the vgm player is targeting is the sn7 soundchip rather than the master system, and the vgm player ignores the computational ability that would be required of the master system (which is does not have) to recreate the tune. think of it like how there will be computational tricks that the atari st can do with the ym, that the spectrum 128 cannot do with the ay, though the chips are in essence the same. sorry