“...The triremes began to run foul of each other, or become entangled with the store-vessels: so that in every ship the men aboard were obliged to keep pushing off their neighbors on each side with poles, not without loud clamor and mutual reproaches, which prevented both the orders of the captain, and the cheering sound or song whereby the keleustês animated the rowers and kept them to time, from being at all audible. Moreover, the fresh breeze had occasioned such a swell, that these rowers, unskilful under all circumstances, could not get their oars clear of the water, and the pilots thus lost all command over their vessels.(1)

(1) See Dr. Arnold's note upon this passage of Thucydidês, respecting the keleustês and his functions: to the passages which he indicates as reference, I will add two more of Plautus, Mercat. iv, 2, 5, and Asinaria, iii, 1, 15.

When we conceive the structure of an ancient trireme, we shall at once see, first, how essential the keleustês was, to keep the rowers in harmonious action,?next, how immense the difference must have been between practised and unpractised rowers. The trireme had, in all, one hundred and seventy rowers, distributed into three tiers.”
[History of Greece, vol.6, Grote, 1859]