Here’s the part that explains the click: the play head didn’t glide sideways along the tape the way a cassette head does across a full side. Instead, it stayed put and shifted up or down to line up with each of the four programs in turn. A thin strip of metallic foil, spliced into the tape at the seam where the loop joined itself, told the player exactly when to make that shift — it brushed a sensor contact, and the head clunked into position for the next program.
The catch was math, not malfunction. Record labels had to divide an album’s total running time into four roughly equal chunks to fit the format, and songs almost never lined up neatly with those quarter-marks. So a track would often run right up against the switch point, get interrupted the instant the foil sensor did its job, and then keep going — same song, next program — a beat or two later. That’s the cut-and-resume everyone remembers: not a glitch, just four programs of music physically stitched together on a single loop of tape.
