It works within Windows either because you've got the WDM driver installed, as this uses 220-5-1 emulating an SBPro as part of the WDM specification, or you've got the VXD drivers installed, as this uses the settings in the soundcard's tab in Windows Device Manager under Dosbox settings and emulates an SB16 using 220-7-1-5-330-T6. This is, by the way, much better than the WDM driver for dos within Windows as far as compatiblity with games, FM emulation if the game doesn't have MPU-401, sound quality, etc. I don't use it these days as WDM drivers are much better for all Windows audio.
The reason it probably doesn't work in MS-DOS Mode is that your motherboard doesn't support non-maskable interrupts. All the Ensoniq PCI, SB 16 PCI, SB 64 PCI, SB 128 PCI, SBLive, Audigy 1 and 2 cards need this support from the motherboard. Most newer motherboards do not support this.
Surprise! My Epox EP-8KRAIPRO does. I was shocked when my Audigy 2 ZS, using the MAME SBLive Dos drivers and the Audigy12.EXE program passed that SBEGO test and also worked with all the games that I used to get working with my SBLive on my older motherboards.
I had a problem getting 98SE working so now it's just XP and Vista with VMWare for 98, but I'm about to attempt a real 98 install again. Now that I know I can use real dos with this board I can''t resist trying. If 98 zonks out with the stupid IOS error at startup again (Real Mode Memory Allocation Failed) I may just keep a small MS-DOS 6.22 partition just to use the real dos mode for the Audigy 2 ZS. Gosh, it sounds much better than my old SBLive's did!
By the way, Dosbox is awesome but my games that do work with the Live Dos drivers just seem to synch better in real dos than in the Dosbox program. Meaning, mouse dependant stuff, better sounding, audio/video synch, etc.