Perhaps. As a former orchestral musician I would say the behavior comes from the need for there to be a leader — if all that is happening is a cacophony of soun

Perhaps. As a former orchestral musician I would say the behavior comes from the need for there to be a leader — if all that is happening is a cacophony of sound, no one has taken the reins as the tempo-keeper and everyone is either not paying attention or just confused. By joining with one of the other inputs, you create a majority or at least a plurality, and then the expectation is the other musicians will adjust to join the plurality. You might also increase volume or exaggerate movements to get everyone on board.