Over 40 melodies, most of them fragmented, have survived as stone
inscriptions or musical papyri (scraps of papyrus, the ancient
equivalent of paper) containing musical notation. While it is
certainly true that the hearings are lost recent research has
satisfactorily deciphered Ancient Greek Music AGM notation and
rhythm.
In AGM scripts, above each line of Greek is notation that looks
mostly like Greek letters, but is in fact vocal musical notation.
Interestingly, as it has been mentioned before, ancient musicians
had two completely separate systems of musical notation, the one
meant for voice, and the other for instruments