The way Calchas is introduced in Agamemnon

Dec 2017
I am confused by the shift from the Chorus' ignorance to the sudden power to speak of omens.

I am reading a simpler english translation by someone named Peter Arcese. Calchas saying he possesses the power to speak of omens is called Strophe 1. Another translation doesn't separate this at all as you can see here: Tragedies. Literally translated with critical and illustrative notes, and an introd. by Theodore Alois Buckley

The online oxford dictionaries definition of Strophe doesn't help; 1. In Greek choral and lyric poetry, and imitations of this: A series of lines forming a system, the metrical structure of which is repeated in a following system called the antistrophe n. Also, in wider sense, one of two or more metrically corresponding series of lines forming divisions of a lyric poem. Hence occasionally (after French) used with reference to modern poetry as equivalent to stanza n.
Originally the word στροϕή, ‘turning’, was applied to the movement of the chorus from right to left, and ἀντιστροϕή, ‘counter-turn’, to its returning movement from left to right; hence these terms became the designations of the portions of the choric ode sung during these movements respectively.

Someone tell me how they read this part its got to be too simple. what am i missing:deadhorse::sad: