I finally bought myself and old audio cassette player. The insides look crazy clean and the drive belts seem neither loose nor dried out.

But!

It's only the left "axis" - or whatever it's called - that's spinning and thus "driving/forwarding" the tape. With "left", I mean the one that rolls up the tape as it's being played. Looking inside, the right axis is not even actuated. It's just a "dead"/unmoving part. Is this how they all work?