Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
It is by the raising, lowering or inflexion of the voice that the orator stirs the emotions of his hearers, and the measure, if I may repeat the term, of voice or phrase differs according as we wish to rouse the indignation or the pity of the judge. For, as we know, different emotions are roused even by the various musical instruments, which are incapable of reproducing speech.
Further the
To proceed, an orator will assuredly pay special attention to his voice, and what is so specially the concern of music as this? Here too I must not anticipate a later section of this work, and will content myself by citing the example of Gaius Gracchus, the leading orator of his age, who during his speeches had a musician standing behind him with a pitchpipe, or tonarion as the Greeks call it, whose duty it was to give him the tones in which his voice was to be pitched.