> otherwise the innermost rings would have a far faster rhythm. Think that over. On a 33 1/3 LP, the outermost groove takes 1.8 seconds to complete a rotation

> otherwise the innermost rings would have a far faster rhythm. Think that over. On a 33 1/3 LP, the outermost groove takes 1.8 seconds to complete a rotation. The innermost groove takes... 1.8 seconds to complete a rotation. Hence, over the entire record, every single groove lines encodes 1.8 seconds of information and lines up exactly with its neighbor in terms of time elapsed. The inner grooves have less space to cover but they compensate by moving more slowly. It's weird but makes sense in a way that's reminiscent of Aristotle's wheel paradox ( https://en.wikipedia.org/wiki/Aristotle%27s_wheel_paradox https://en.wikipedia.org/wiki/Aristotle%27s_wheel_paradox ) On a perfectly mastered LP, any song whose bpm is a multiple of 33 1/3 would have these lined up rhythmic patterns. E.g. a song that clocks in at 100 bpm would have exactly 3 beats in every rotation. You could make a faster dance song line up by speeding up the motor to a fractional degree. >Incidentally, a lot of sound engineers at the time would put tracks with less frequency dynamicism into those innermost rings to prevent records from skipping. True, since the innermost grooves have less space to encode information, they have to wobble more in a given distance in order to maintain the same dynamic range. IIRC sometimes they would space those inner grooves further apart to give them more wobble room.