“Next in turn are two "oar-masters" (toixarchoi), who are each responsible for the discipline and working of one of the long rowers' benches; and following in grade, though highly important, are the keleustes, and the trieraules, who, by voice and by flute respectively, will give the time and if needs be encouragement to the rowers. These are all the regular officers, but naturally for handling the sails and anchors some common sailors are desirable. The Invincible carries 17 of these….
[A Day in Old Athens, Davis, 1914, pp.131-132]