hi pster, there's a regular rhythm, it just doesn’t always correspond to the longs which is perhaps what is tricking your ear, instead it corresponds to the march in these marching anapaests. i’ll try to explain how you can practically get the rhythm (you actually need to march to it and then it becomes clear):
to take a step back, this is a marching anapaest section. martin west explains in his studies on aeschylus (pgs 8 to 9) something interesting – you can actually guess how the greek chorus moved on stage by calculating from the length of this marching anapaest section. each metron of 2 anapaests (short short long, short short long) corresponds to a double pace. i’ll explain the double pace bit in a tic, this is the key to getting the rhythm, but to continue with the interesting bit – if you assume the double pace was about a metre, then you can calculate that the chorus marched onstage to about 30 metra (i.e. 30 double paces) and then did 2 laps of the orchestra (each lap around 40 to 45 metres) because there are 119 metra in this section. The number of metra in the marching anapaest section of his persians is about the same as in agamemnon, 119 metra (corresponding to an entry plus 2 laps), whereas the number of metra in the marching anapaest section of his suppliants and ajax correspond to an entry plus 1 lap (74 in suppliants, 72 in ajax).
back to the rhythm. imagine the metron of 2 anapaests (short short long, short short long) has 8 beats, each short having 1 beat and each long having 2 beats. each of these corresponds to a double step of the marching chorus, and each step falls in the long (or the princeps bit), i.e. on beats 3 and 7 (the first beat of each long) – see martin west’s greek metre 1982, pg 53.
try actually marching to line 40 like this:
40 δέκατον μὲν ἔτος τόδ´ ἐπεὶ Πριάμωι
first foot down on the beat 3 (-τον in δέκατον), second foot down on beat 7 (-τος in ἔτος) and so on.
the next trick is that in marching anapaests you can change an anapaest (short short long) into a dactyl (long short short) but the marching rhythm stays the same (first foot down on beat 3, second foot down on beat 7), so now your first foot goes down on a short syllable, not a long - that's what tricks your ear. march it though and it's fine.
so to take the line that’s bothering you:
44 τιμῆς ὀχυρὸν ζεῦγος Ἀτρειδᾶν,
- first foot down on the beginning of μῆς in τιμῆς (this is a spondee, 2 longs so 4 beats in itself),
- second foot down on beginning of ρὸν in ὀχυρὸν,
- first foot down on γος in ζεῦγος (this is where your ear can trick you because you are used to feet going down on the longs in anapaests, but here instead of an anapaest here you have the dactyl ζεῦγος Ἀ-, and the foot still goes down on beat 3 being the first short in the dactyl, ie γος in ζεῦγος)
- second foot down in δᾶν in Ἀτρειδᾶν
to tie this all back to the recording (which just arrived for me yesterday), they are drumming on the beat where your foot goes down.
try actually marching this out as you are pronouncing it or as you are listening to the recording and the rhythm will become clear.
none of this has anything to do with an ictus, i.e. you don't stress or do anything special with your voice on beats 3 and 7 in each metron, it’s just the marching rhythm. you should read the marching anapaests of the spartans in martin west’s greek metre pg 53 to really get the feel for marching anapaests: ἄγετ', ὦ Σπάρτας εὐάνδρου | κοῦροι πατέρων πολιητᾶν, with the marching feel falling on first foot - ὦ, second foot – τας in Σπάρτας, first foot – άν in εὐάνδρου, second foot in the pause after εὐάνδρου, and so on.
as to your second question, i think the guys who did the recording are classicists and so they will likely not have as good a musical ear for getting the rhythm right as you, i go easy on anyone who has a go at doing this stuff for us, even if it's not exactly how i would do it, i still think it's invaluable. i think the pause you mention at the beginning of Μενέλαος is just him taking a breath. cheers, chad