[Stephen]

It's not all that complicated.

Every time a cassette or VHS is played or copied the head runs against the tape, so over time it decreases in quality, so what you had on its first play is not the same as what you get after the 100th play. Whether it's video or audio.

Same with vinyl records. You have a needle going through the grooves and over time that's how you can end up with static or pops and crackles.