Back in the forties, fifties, and sixties, before the days of DC servo motors, capstans on professional audio recorders were driven by AC synchronous motors, which locked to the frequency of the incoming power, which was as good a frequency reference as most people could afford. Your electric clocks always kept perfect time, didn't they? The problem with this was that if you wanted to run your tape recorder a little bit off speed for some reason, you had to provide AC power to the capstan motor at a frequency that differed from 60 Hz by the amount you wanted to change the speed. This was usually done with an oscillator driving a special-purpose amplifier that had the capability of putting out approximately 117 volts with sufficient current to drive the motor. The whole system was called a variable speed oscillator, or VSO. It was expensive enough that small recording studios like the one I was working for in 1968 usually didn't own one. But for a fixed speed change, as long as it was only a small change, we could wrap the capstan with a layer or two of splicing tape, which would increase the effective diameter of the capstan, and therefore tape speed, by a small amount. Sometimes somebody would decide that a song "dragged" or needed "brightening up" and the solution was to "give the capstan a wrap" and make a dub. Must have driven people with perfect pitch nuts, like the Top 40 radio stations that would speed up their turntables a few per cent so they'd sound more exciting than their competition. Anyway, the technique could be used in reverse if you wrapped the capstan of the record deck instead of the playback deck, and that's how I (approximately) corrected the pitch of the beach recordings.