The Abyss + Strionic Resonator

[Malchar]

If I control the abyss and strionic resonator, and my opponent controls a veteran explorer and a primeval titan. During my opponent's upkeep, the abyss's ability is put on the stack targeting veteran explorer. I activate strionic resonator targeting the abyss's ability. For the copy, can I change the target to primeval titan?

It seems like the text on resonator means that I get to choose the target. However, on the abyss's ability, it says "target .. of his or her choice". Is that a targeting restriction similar to the nonartifact requirement? Is it that the abyss's ability can only ever target something of the opponent's choice, or can the target be theoretically changed after the opponent makes the initial choice?

[rufus]

...
It seems like the text on resonator means that I get to choose the target. However, on the abyss's ability, it says "target .. of his or her choice". Is that a targeting restriction similar to the nonartifact requirement? Is it that the abyss's ability can only ever target something of the opponent's choice, or can the target be theoretically changed after the opponent makes the initial choice?

The target gets copied, and the you may change it to the other creature. The opponent doesn't get to chose a target again at all. The abyss is weird, but the 'choose a target' template is also on stuff like Chain of Plasma that can obviously get misdirected.

[cdr]

You can change the target. Who makes the choice on the ability is not a restriction.