> which would mess with the vertical-blanking signal in a way that wasn't particularly noticeable on playback, but would mess with VHS recording On a related n

> which would mess with the vertical-blanking signal in a way that wasn't particularly noticeable on playback, but would mess with VHS recording On a related note, one of the copy protection systems I put on some Sinclair Spectrum cassette games involved changing the baud rate part way through loading. It was over 35 years ago so the details are hazy, but I had a custom "master maker" to play the audio[1] and at a specific byte count would change the frequency. The mastering and duplication machines coped with it fine and the loader was written to expect it, but it threw out most home tape to tape systems for reasons I can't exactly remember. [1] These were usually recorded directly from the Spectrum onto 2 inch reel to reel tapes in a studio, that was then used as the master at the duplicators.