Sounds like you could be having PnP issues, with Win95 re-allocating resources in such a way as causing conflicts not present at boot (after BIOS did its PnP). The MMSN810 itself is non-PnP, so the problem is with something else on IRQ5 or DMA1 (assuming you set those values in the EEPROM config for the card). I'd try to figure out what is using those resources under Win95 and move it.

Unfortunately, I have not been able to find resources conflict. I turned off almost all devices. There are only two com devices (for the mouse), a keyboard, some system devices (timer, dma), a video card, even the system is loaded from the CF-IDE adapter, on which a special address is set. FDD and IDE and the parallel port on the multicard are disabled with jumpers. I tried to turn on the automatic resource setting for the sound card, then with the help of SGP16FIG.EXE I wrote the same values ​​into the card's memory. I can even run DEMOFM.EXE and SG3.EXE under Windows, and they will work. DEMO.EXE won't work, crashes. SG3.EXE plays almost everything, except for "SG 8-bit" sample (just crashes) and "SP VOICE" (warns about the ms-dos compatibility mode and the sound is ragged). Do I need to keep the settings for the sound card in autoexec.bat and config.sys?
Resources configured as:
I/O 0220-022F
I/O 0604-060B
I/O 0388-038B
IRQ 10
IRQ 11
DMA 03
DMA 01

SGP16FIG.EXE shows stored settings
Wave port base address...604H
SG/MIDI Base address.....220H
SG/MIDI IRQ Setting IRQ..10
DMA Channel Setting DMA..3
Game Port Setting........ENABLE
AT-BUS CD ROM Setting....PANASOINC
CD ROM Address Setting...320H

Those are some pretty eccentric settings. It's entirely possible that you now have no conflicts, but that the software simply can't use it.

I'd suggest doing it the other way round:
- set default resources on card via non-PnP SGP16FIG:
Base Address 220H
IRQ 5 (or maybe 7, if LPT2 is disabled and you have good reason not to use 5)
DMA 1
WSS 530H
and unless you're actively using it, disable CD ROM and game port.
- be sure to reserve IRQ5 for non-PnP in BIOS
- then see if it works in DOS. That should be no problem.
- then try in Windows. If it fails look for conflicts. Randomly disabling stuff isn't the best way, let Windowns help you here:
http://midi.teragonaudio.com/tutr/conflict.htm

Go into Control Panel, run the System utility, and turn to the Device Manager page. Click on the Print button. Ask for a "System Summary".

That gives you a list of IRQs with what is on them. If you see two on IRQ5 you know what's causing the problems.