I remember reading somewhere about rowing at different tempos depending on a number of different criteria. If you had a long way to go you would row at a tempo that would conserve your strength. If you had a need for speed you rowed at a faster pace. If the weather was rough then there was another pace that differed from a calm water pace. The coxswain was the expert and the pace of his song told the rowers how fast to row.

I think this was from a tract on the shore based whaling industry off one of the Atlantic islands.