I always had to have a reel-to-reel tape recorder to monkey with, when I was a kid. These became a little scarce with the advent of cassette tapes, but you could still get the little reels of tape for them at Radio Shack. They were much preferable to cassettes, because you could slow them down with your finger, or otherwise tweak them.
I was fascinated by all the little rollers and plastic gears. Electronics just don’t have that smell of industrial lubricant and extruded plastic these days, and I kind of miss it. When my son was little I took apart the VCR we had because an Army Man was keeping the tape carriage from moving, but it just wasn’t the same. Maybe they use a different grease these days.