bdp24,
As I stated above, I don't know why the idler tables I heard have the kind of "drive" that they do have, but, I suspect it has to do with the high torque motors employed. I have heard the same sort of sound from the three motor Audio Note table and it is a belt drive table, but, it employs three massive motors, each of which supposedly is a 2 hp motor (three massive power supplies are also used to power the motors).
It would be interesting to hear what a modern idler table sounds like. I would love to hear the Galibier table.