Full Idea
In singing and playing the lyre, a boy will be likely to reveal not only courage and moderation, but also justice.
Gist of Idea
Musical performance can reveal a range of virtues
Source
Damon (fragments/reports [c.460 BCE], B4), quoted by (who?) - where?
Book Reference
'Ancilla to the Pre-Socratic Philosophers', ed/tr. Freeman,Kathleen [Harvard 1957], p.71