So, what IS the magic of idlers? I think it must be inertia related. Not the inertia of a heavy platter got up to speed by a belt and mass/low friction bearing keeping the platter gently ticking along. It must be something to do w the moment of force applied, and that a continuous motive push urges the platter on. The result in both cases is ostensibly the same: 33.33rpm with as minimal drift as possible. But the keeping speed going versus allowing the speed to maintain, has dramatically different outcomes on the sound we hear.