If it's the once-popular emulator that has been out of date for over a decade, all it is is recording THE EMULATOR'S audio output to a WAV file. (so if the emulator's audio quality is poor, which it is, or the emulator lags, which is oddly enough seems to do MORE the FASTER your CPU is, you'll bad AND laggy audio that is not at all accurate to game)
You're not actually taking anything FROM the ROM.
From what I understand, getting a proper SPC rip is not as simple as hitting a button in ZSNES.
To get a PROPER rip, you'd have to actually know about the sound data and how to find it in the ROM (I don't).