Tiberius and Caius Gracchus

Hence men like Drusus found fault with him because he bought silver dolphins at twelve hundred and fifty drachmas the pound. Again, their tempers were no less different than their speech. Tiberius was reasonable and gentle, while Caius was harsh and fiery, so that against his better judgment he was often carried away by anger as he spoke, raising his voice to a high pitch and uttering abuse and losing the thread of his discourse.

Wherefore, to guard against such digressions, he employed an intelligent servant, Licinius, who stood behind him when he was speaking, with a sounding instrument for giving the tones of the voice their pitch. Whenever this servant noticed that the voice of Caius was getting harsh and broken with anger, he would give out a soft key-note, on hearing which Caius would at once remit the vehemence of his passion and of his speech, grow gentle, and show himself easy to recall.