I had been holding at Colts Neck VOR in the New York ATC system for about an hour which was not uncommon in the late '60s with others arriving in early evening from the South and the Caribbean.
One of the co-pilots in the holding pattern asked us to monitor a discreet frequency, on which he asked all the aircraft their position and speed in the hold, then asked if they could increase or decrease their speeds slightly. Eventually, he got all the aircraft turning over the VOR, to start a new outbound leg, at the same time!
We heard the controller shout, "Hey! Where are all my aeroplanes? I've just got one great big blob!"