A few details. Creative Labs did not completely drop Game Blaster support with the Sound Blaster 1.5, they just started selling the two Philips SAA 1099 chips separately. The sockets are still present on Sound Blaster 1.5 and 2, but not on the later models.
The MPU-401 is only an interface, not a synthesizer. DOSBox does emulate it, it has to, not only for the MT-32 games, but for the General MIDI games as well.
The MPU-401 can act as a sequencer and several other basic MIDI functions. This is known as intelligent mode. This, too, is emulated by DOSBox since 2004.
http://vogons.zetafleet.com/viewtopic.php?t=4282
And it’s LAPC-I, not LAPC-1, but that’s a very common mistake, found in some contemporary sound configuration utilities as well. 