I don't know how hard this would be, but it doesn't seem like Classic WoW has a radically different directory structure from Retail, so hoping that making MuteSoundFile compatible with Classic is possible.

Muting fizzle and wand sounds is sorely needed in it.

Thank you for working on this addon nevertheless.

Not possible unless Blizz backport the functionality from retail. But the old "replacing sounds" way works.