it all comes down to resources
lets say the AWE is on Port 220, IRQ 5, DMA 1, High 5
and the YMF is on Port 240, IRQ 7, DMA 6 High 3

As long as the dos game allows you to select the card/settings you can tell it which port to use, say doom you would set it up something like
SFX= Sound blaster on Port 220
Music= General Midi on 240

Windows is a bit easier, go to device manager and select the primary device for sound and music and the game will usually default to that.
Some games wont play nice and force you to use the same card for everything, every now and then a game also may not like 2 soundacards for whatever reason.
If that's the case you can always disable one from device manager or not load the drivers in a dos boot menu

But a lot of us have 2 cards in a PC like this. PCI card for windows and ISA card for dos. My Slot 1 actually has 3 cards Onboard Yamaha YMF, Audigy 2 and AWE64 and all play nice.

PS I'm not saying use those specific settings, It'll depend on what works in your system, PCI cards especially can be very picky on what they'll work on

I was considering myself using SB AWE64 for digital sounds and using yamaha YMF744 card for getting opl3 in dos instead of the awe64 music. Is there any reason why this would not work?

Thats still fine, just as long as you point the games setup to the AWE's resources for digital sound and the Yamaha for the music .
Any game that only allows you to select 1 device for both sound and music you'll have to pick one card or the other though.

oh and Adlib games will use both cards simultaneously, just make sure to mute the card you don't want

Better yet, disable the AdLib port on the AWE64 which is possible to do in both DOS and Windows. This way you won't need to be adjusting the mixer of both sound cards in case you want to use the EMU8K capabilities of the AWE64.

chinny22 wrote on 2022-05-15, 15:53:

But a lot of us have 2 cards in a PC like this. PCI card for windows and ISA card for dos. My Slot 1 actually has 3 cards Onboard Yamaha YMF, Audigy 2 and AWE64 and all play nice.

Can I know how your end device, the speakers, is resolved? Each soundcard its own set or some sort of mixer?

Ydee wrote on 2022-05-16, 10:44:

chinny22 wrote on 2022-05-15, 15:53:

But a lot of us have 2 cards in a PC like this. PCI card for windows and ISA card for dos. My Slot 1 actually has 3 cards Onboard Yamaha YMF, Audigy 2 and AWE64 and all play nice.

Can I know how your end device, the speakers, is resolved? Each soundcard its own set or some sort of mixer?

Typically I just use 1 card per game and have audio extention cables that I plug the speakers into. The rare times I do want to use 2 cards I have a 2nd set of speakers I can use.
Most people though connect line out from 1 card to line in of the other card which also has the speakers attached.

Thank you for the information, I will definitely use it in my machines with ISAs and PCI soundcards.

I am rocking very similar spec with three sound cards (link to specs). In DOS I use AWE32 and GUS simultaneously on regular basis midi/opl music from AWE32 and sfx through GUS. In Windows Me I use third sound card: Aureal Vortex 2 for some 3d sound goodness.
All of them are working well together, it is just a matter of good resource allocation especially in DOS, Windows can do IRQ sharing and is more forgiving.
Later I have added an adaptec PCI scsi controller card which also coexists nicely. The trick to all of this hardware working in DOS is extensive use of loadsys tool and numerous bat files I have created to load or unload drivers for different occasions (cdon, cdoff, ftpon, ftpoff, scsion, scsioff etc.)
To mix all the audio outputs I use: Maker Hart LOOP MIXER

Cheers.

Ydee wrote on 2022-05-16, 10:44:

chinny22 wrote on 2022-05-15, 15:53:

But a lot of us have 2 cards in a PC like this. PCI card for windows and ISA card for dos. My Slot 1 actually has 3 cards Onboard Yamaha YMF, Audigy 2 and AWE64 and all play nice.

Can I know how your end device, the speakers, is resolved? Each soundcard its own set or some sort of mixer?

I have quite a few systems, many of which with multiple cards. The daisychain-option (line out from one into line in on the other) never really worked for me, always had noise issues and got irritated by having to mess around with mixer settings every time I swapped a card. Instead I hook it all up to a mixer (Behringer RX1602 in my case - highly recommended)