This had never been explicitly addressed in the BotB's Lyceum article, so it isn't technically disallowed (and it's what i actually suggested here
as one of the methods to render directly from FL.
Ideally we would brainstorm on whether or not this should be allowed or not and add an appropriate notice in the format rules, but i'm not sure if most of people here care enough about MIDI/know enough about MSGS.
The thing with Windows' internal synthesis is that there's two ways to access the MSGS sound set in Windows
, either the regular one via the old MME midiOut API or a different one, introduced later and now technically deprecated but still working - through DirectX's DirectMusic. It seems that currently barely any software supports picking between those two and defaults to MME midiOut but old Winamp
and FL Studio (through Fruity LSD) can still make use of it.
DirectMusic seems to be rendering with its own synth engine, merely using the same gm.dls wave bank (by default, since this can be controlled and some games like Gothic and Gothic 2
actually made use of DM with custom banks loaded, to create dynamic soundtracks), which is why the usual polyphony limit is bypassed.
BTW I'm actually curious about the polyphony of the bare MSGS you mentioned - did it actually change over the years with the subsequent versions of Windows? Or maybe you just used to play it via the DirectMusic API before and never noticed/knew, which would explain why. I'm curious tbh.