This is a fragment of the play Orestes, written by Euripides (c 480-406 BCE). The fragment is thought to have been written around 200 BCE. It is the text of the first chorus (verses 338-344 for the classicists out there). The marks above the text are musical notations. For more on the fragment, see the World Digital Library page for this item.
Ok, everybody, all together now:
τίς ἔλεος, τίς ὅδ᾽ ἀγὼν
335θοάζων σε τὸν μέλεον, ᾧ δάκρυα
πορεύων τις ἐς δόμον ἀλαστόρων
ματέρος αἷμα σᾶς, ὅ σ᾽ ἀναβακχεύει;
340ὁ μέγας ὄλβος οὐ μόνιμος ἐν βροτοῖς:
ἀνὰ δὲ λαῖφος ὥς
τις ἀκάτου θοᾶς τινάξας δαίμων
κατέκλυσεν δεινῶν πόνων ὡς πόντου
λάβροις ὀλεθρίοισιν ἐν κύμασιν.
345τίνα γὰρ ἔτι πάρος οἶκον ἕτερον ἢ τὸν ἀπὸ
τὸν ἀπὸ Ταντάλου, σέβεσθαί με χρή;
O Zeus! What pity, what deadly struggle is here,  hurrying you on, the wretch on whom some avenging fiend is heaping tears upon tears, bringing to the house your mother’s blood, which drives you raving mad?  Great prosperity is not secure among mortals. I lament, I lament! But some divine power, shaking it to and fro like the sail of a swift ship, plunges it deep in the waves of grievous affliction, violent and deadly as the waves of the sea.  For what other family must I still revere, rather than the one from a divine marriage, from Tantalus.]
(from Euripides. The Complete Greek Drama, edited by Whitney J. Oates and Eugene O’Neill, Jr. in two volumes. 2. Orestes, translated by E. P. Coleridge. New York. Random House. 1938.)
Sound like opera? You’re right: the story has been turned into an opera by Handel (who used the story as told by Euripides), Sergeiy Taneyev (NY Times article on it here) and Iannis Xenakis (both of whom used the version of the story told by Aeschylus).
Image attribution: Orestes 338-44 via the World Digital Library. http://www.wdl.org/en/item/4309/#q=classical+music