You have to put a decoding chip in the cassette device... or but the audio cable in the line-in of a pc and decode it there... but then I think I'd say, why bot

You have to put a decoding chip in the cassette device... or but the audio cable in the line-in of a pc and decode it there... but then I think I'd say, why bother. Stick with audio and analog for tapes (except when you are using a C64 and record data from radio or modem). Not sure if a wav decoder has been done for C64... Opus and mp4 are out of it's league (not sure about running it in an emulator on faster hardware).