Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
Indeed nature itself seems to have given music as a boon to men to lighten the strain of labour: even the rower in the galleys is cheered to effort by song. Nor is this function of music confined to cases where the efforts of a number are given union by the sound of some sweet voice that sets the tune, but even solitary workers find solace at their toil in artless song.