On OS X, if you go to System Preferences > Dictation and Speech, then select “Customize…” under System Voice, you can download or upgrade your Greek voices. There are a male and female voice you can try: Nikos and Melina respectively.

There are two ways I know of that you can then get those voices to read Greek for you.

The first way is, with Nikos or Melina selected as the System Voice, you select any Greek text in another app (such as TextEdit), right click and select Speech > Start Speaking. This will honour the speed setting in System Preferences > Dictation and Speech. Slowing down the speech drops quality dramatically, though.

The second way is on the command line with say. I can’t work out if say supports slowing down the reading (it doesn’t honour the speed setting in System Preferences) but it does support outputting the result to an AIFF file.

Note that you can’t feed it polytonic Greek so you need to strip breathing and convert accents. I did that to produce a text like this:

Ήν δέ άνθρωπος εκ τών Φαρισαίων, Νικόδημος όνομα αυτώ, άρχων τών Ιουδαίων· ούτος ήλθεν πρός αυτόν νυκτός καί είπεν αυτώ· Ραββί, οίδαμεν ότι από θεού ελήλυθας διδάσκαλος· ουδείς γάρ δύναται ταύτα τά σημεία ποιείν ά σύ ποιείς, εάν μή ή ο θεός μετ’ αυτού. απεκρίθη Ιησούς καί είπεν αυτώ· Αμήν αμήν λέγω σοι, εάν μή τις γεννηθή άνωθεν, ου δύναται ιδείν τήν βασιλείαν τού θεού.

I then used

say -v Nikos -f john_3_1.txt -o john_3_1

to produce the following AIFF file.

A pretty decent reading of the Greek New Testament with Modern Greek pronunciation.

The only oddity is that the ου in the last clause is spelled out. Not sure how to fix that.

What excites me about this is less the generation of long audio files of entire passages, but more how it could be used in conjunction with an intelligent tutor to pronounce individual words and phrases that the student is currently studying.