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Hi Don, Revolution occurs around a point outside of its geometry. Rotation occurs around a point within its geometry. i.e. planets (at least in our solar system!) revolve around the sun but each rotates around its won axis. When a disk is spinning its action is analagous to a planet that's rotating. For it to be revolving, the phonograph would have to be on a 'lazy susan' that's spinning: now that'd be a source of rumble! Best, Shiffy