As I read the play in Gilbert Murray’s translation, I will use his spellings (Latinised names such as Clytemnestra, rather than Greek transliterations such as Klytaimestra).
1/ Among the ancient Greek plays that survive today about the killing of Clytemnestra (Klytaimestra), the first was Aeschylus’s Libation Bearers, part of the Oresteia, first performed in 458 BC.
Sophocles and Euripides, from the same generation, both wrote a play named Electra, though it’s not certain which one came out first: the one by Euripides was written in the mid-410s BC, the one by Sophocles is dated around 420–414 BC (wouldn’t it have been funny though if they were first performed the same year?).
These two Electra plays don’t seem to reference each other, but there’s one scene in which Euripides clearly mocks a scene in Libation Bearers: how could Electra recognise Orestes from some strand of hair, or footprints? Don’t be ridiculous, Aeschylus.
2/ Like Sophocles, Euripides focuses on the character of Electra.
“ELECTRA […] Brother, brother, on some far shore
Hast thou a city, is there a door
That knows thy footfall, Wandering One?
Who left me, left me, when all our pain
Was bitter about us, a father slain,
And a girl that wept in her room alone.
Thou couldst break me this bondage sore,
Only thou, who art far away,
Loose our father, and wake once more…
Zeus, Zeus, dost hear me pray?...
The sleeping blood and the shame and the doom!
O feet that rest not, over the foam
Of distant seas, come home, come home!”
Sophocles’s Electra is a larger-than-life character: striking, intense, deformed by hate. Euripides’s Electra appears more vulnerable and fragile.
One of the changes Euripides makes is that Clytemnestra and Aegisthus (also known as Aigisthos) don’t imprison Electra, but marry her off to a poor peasant so that she doesn’t have the power to wage war against them. She’s stripped off the position of princess. The peasant however doesn’t sleep with her, out of respect for her and her father. We then have this interesting passage:
“ORESTES How dark lies honour hid! And what turmoil
In all things human: sons of mighty men
Fallen to naught, and from ill seed again
Good fruit: yea, famine in the rich man’s scroll
Writ deep, and in poor flesh a lordly soul!
As, lo, this man, not great in Argos, not
With pride of house, uplifted, in a lot
Of unmarked life hath shown a prince’s grace…”
Not hard to see why some people call Euripides modern.
3/ In this play, Orestes is much weaker and more passive. The old man who rescued him as a child is now the one to come up with the plan to kill Aegisthus. The plan to kill Clytemnestra comes from Electra.
Orestes hesitates.
“ORESTES ’Tis my mother comes: my own
Mother, that bare me.
[…]
ORESTES What would we with our mother? Didst thou say
Kill her?
ELECTRA (turning on him) What? Is it pity? Dost thou fear
To see thy mother’s shape?
ORESTES ’Twas she that bare
My body into life. She gave me suck.
How can I strike her?”
(The word “bare” is in my copy, shouldn’t it be “bore”?).
“ORESTES I was a clean man once. Shall I be thrust
From men’s sight, blotted with her blood?
ELECTRA Thy blot
Is black as death if him thou succour not!”
Euripides humanises Orestes and removes Apollo—there is no command from the gods—it is Electra who pushes Orestes into it.
Like Sophocles, he lets us see Electra’s point of view and then shows us Clytemnestra’s: not only did Agamemnon kill her daughter Iphigenia…
“CLYTEMNESTRA […] Nay, for long,
I never would have killed him. But he came,
At last, bringing that damsel, with the flame
Of God about her, mad and knowing all;
And set her in my room; and in one wall
Would hold two queens!...”
In a way, Aeschylus sees and depicts the tragedy from a distance; Sophocles and Euripides come close to the characters and depict their clashing perspectives; both give us a confrontation between mother and daughter.
4/ Sophocles’s play focuses on Electra’s state of mind that leads to the killing. Euripides’s play has the revenge, and also depicts the horror of Electra and Orestes when they realise what they have done.
“ORESTES Saw’st thou her raiment there,
Sister, there in the blood?
She drew it back as she stood,
She opened her bosom bare,
She bent her knees to the earth,
The knees that bent in my birth…
And I… Oh, her hair, her hair…
(He breaks into inarticulate weeping)”
I would guess that Euripides’s Electra was after Sophocles’s.
There are mentions of gods throughout the play and a god does appear at the end telling what Orestes and Electra have to do to pay for the murder of their mother, but I would say that the play is humanist, not mythic: unlike the characters in Aeschylus’s and Sophocles’s plays, Euripides’s Electra and Orestes choose to kill their mother themselves, without an oracle. A god only appears after the deed is done. Not only so, the killings are more brutal: Orestes kills Aegisthus after being welcomed as a guest to his feast; Electra lures Clytemnestra to the house and pretends to reconcile with her before having her killed.
All three plays are wonderful, in different ways.