Or does the Saturn support audio effects in the CD player? In such a case I would imagine that the audio data would be fed directly into the audio DSP rather than routed through the SH-2s.
I was thinking of the 68000 more than the SH-2s, but I suppose there is a possibility that it is confined within the SCSP. I'd have to re-read various manuals to be more certain, but I'd be surprised if there's no way to get at the data. Still, I agree with you that using audio data is probably not the best way.