Institutio Oratoria

But while exercise, which gives strength in all cases, is equally necessary both for orators and singing-masters, it is a different kind of exercise which they require. For the orator is too much occupied by civil affairs to be able to allot fixed times for taking a walk, and he cannot tune his voice through all the notes of the scale nor spare it exertion, since it is frequently necessary for him to speak in several cases in succession.

Nor is the same regime suitable as regards food: for the orator needs a strong and enduring voice rather than one which is soft and sweet, while the singer mellows all sounds, even the highest, by the modulation of his voice, whereas we have often to speak in harsh and agitated tones, must pass wakeful nights, swallow the soot that is produced by the midnight oil and stick to our work though our clothes be dripping with sweat.