Luckily for the computer cassette tapes, the FSK'ed bits lie way down in the sound spectrum, IIRC circa 1000 Hz. I recently digitized some old favorite audio c

Luckily for the computer cassette tapes, the FSK'ed bits lie way down in the sound spectrum, IIRC circa 1000 Hz. I recently digitized some old favorite audio cassette dubs (TDK SA, most made on really good gear) and apart from atrocious wow-and-flutter, the high-end was completely gone on most, down to about 8K anyway. Tape may still be the safest bet to store data long-term. I've read recently that (burned) CD's over 10 years old are getting iffy. Whereas people are still recovering NASA data off tapes made 45 years ago.