In higan’s sfc/alt/dsp directory is the alternate SMP emulation core, used when the accuracy profile isn’t selected. It apparently depends on a couple of Blargg’s audio libraries which includes… “snes_spc-0.9.0”. Of which blargg boasts:

The accurate DSP passes over a hundred strenuous timing and behavior validation tests that were also run on the SNES. As far as I know, it’s the first DSP emulator with cycle accuracy, properly emulating every DSP register and memory access at the exact SPC cycle it occurs at…

And of course, this is already written as a library, meant to be used in another project. No games required.

My only question is: if snes_spc is that accurate, why does higan not use it in accuracy mode for its own accuracy profile? Is byuu’s DSP somehow more accurate? (I suspect so. It’s not like snes_spc is a fast-moving target, as its first public release is also, AFAICT, its only one.) I don’t want to commit one way or the other without an answer…