Is it possible to get the good old glorious sounds back that RAP-10/MT-32 could produce? (my RAP-10 made music 100 times better than the best AWE-32 could produce in most DOS games)
Two separate issues which require different responses. First, the RAP-10 is a General Midi wavetable device, the MT-32 is not General Midi compatible and uses an older technology only somewhat reliant on the samples used by a wavetable device, which it combines with analogue waveforms.
As you may have noticed, DOSBox has built in MT-32 emulation, but it requires the downloading of copyrighted ROMs to use. Once you have found them, you can set it in the config file. The emulation isn't bad and is certainly much better than the "emulation" of the AWE32.
The RAP-10 card has a general midi wavetable synthesis sound component and a 16-bit digital sound processing component like, but compatible with, the Sound Blaster. DOSBox doesn't emulate the digital component, you can use the Sound Blaster 16 emulation instead. As for the midi, you will have to use whatever midi support you have on your current sound card.
I have the RAP-10 Card somewhere still, but my computer doesn't have ISA slots, so its somewhat useless. Sad
Find a small junk computer with ISA slots. The computer provides power and will reset the card on bootup. DOSBox has a midi interface that can communicate with external hardware. The digital sound processing component will be useless but your current sound card should sound better. The general midi component can be accessed externally with a gameport to midi adapter. Connect the midi in of the adapter to the midi out of your sound card (if it has one.)
Better yet, the midi synthesis of the Roland SC-7 Midi Module and the Roland SCB-7 waveblaster daughterboard is identical to the RAP-10's. (Actually its slightly better because there is no stereo DSP component which shares takes two voices that the midi should use on the RAP-10.) These can be a bit of a task to find but shouldn't be too expensive and easier to use with current technology.