The Seikilos Stele contains the the oldest complete song and dates to c.100 BCE. This video explores how the stele was found and how the song sounds; it is sung at 2:28

As long as you live,
shine forth do not at all grieve,
Life exists for a short while,
Time takes its course.

Hoson zēis phainou
mēden holōs su lupou
pros oligon esti to zēn
to telos ho chronos apaitei.