Reader DJ Larson (Gemini Horror) shared this video, demonstrating Pitch and CV mods for a cassette tape player.

He demonstrates the process with a GE Variable Speed Cassette Dictation Recorder Player, but others have done similar mods with other tape players.

Larson mentions a couple of related videos, which we have embedded below:

Chris Randall’s Voltage-Controlled Cassette Deck:

Simon The Magpie’s DIY Line Out On Anything: