[William Cloud Hicklin]

I wouldn't put it that way. Saruman's Voice seems, after all, to be the one aspect of his abilities he retained, even after his capacity to do "wizardry" was taken from him. Arguably it was already all he had left by the time Gandalf, Theoden & Co confronted him, as Merry observed. I don't think that persuasion, even skillful persuasion, constitutes an exercise of "power" in the same sense, or expended or diminished his power.

But mastery of Orcs requires more than mere persuasion.....