> The question is:
> Does anyone know of an interface used to store data on tape with a computer
> using a regular taperecorder?

Years ago when there were no banners on Internet, I used to find all kind of weird pages regarding McGyver-like hardware tamperings.

IIRC, there was a page explaining how to make backups on videotapes by connecting your VCR to the PC (don't ask how).

Another one (closer to what you are searching for), was using the C64 tape unit (was it called C20? 1531? can't remember), possibly via COM or LPT, for the same purpose.

Don't ask about the URLs, my bookmarks got lost the day I trusted a 1.44 floppy disk to store them. Nevermind, they say mistakes make you wiser.

Good luck.