Very cool project. But Sound Blaster is conspicuously missing from this list.
I'd adapt DOSBox's SB code but it's surprisingly complex - DSP support for the whole gamut of SB cards from the Sound Blaster 1.0 to the Sound Blaster 16 are in the same source file, and extracting the parts that I'd need would be more pain than I'm willing to deal with right now.
TonyTrapp's comment below raises a good point – I've tried to focus on emulating sound cards that are harder to find and are possible to do on the Pico. Old used Sound Blaster compatible cards are still relatively available and affordable, compared to the GUS or genuine MPU-401s with intelligent mode. CMS compatible boards are also hard to find, and Tandy compatible boards that you can plug into a normal non-Tandy PC are solely available via DIY projects.
That said, it's more likely that the project doesn't support it (yet) because it's still much easier and cheaper to obtain a Sound Blaster than any of the other cards, since it was ubiquitous. GUSes typically go for hundreds of Euros these days while SBs can be had for much less than hundred.