Think about the object
A cassette has two physical sides and a tape transport. A compact disc has a visible playing surface and a track-based interface on its player. Each format gives you different labels, controls and storage details to document.
Describe the experience you want
A side-long sequence, a handwritten track list, a particular player’s controls or an album’s packaging may be the reason you enjoy a format. Write that reason down rather than assuming another collector shares the same priorities.
Match media and equipment
Use the exact player documentation when checking supported media and functions. Keep irreplaceable recordings separate from experiments with an unverified machine. A useful collection is one you understand, not simply one with more objects.