When Anakin defeats Dooku in their light saber duel in Revenge of the Sith, it seems like Anakin is not really convinced that killing Dooku is the right thing to do. If left unprompted it appears Anakin might very well take Dooku captive as Jedi morality dictates. However, Palpatine finally commands Anakin to kill Darth Tyranus in the same evil wizard vocal style that he uses when he's acting as Darth Sidious rather than when he speaks using his friendly 'Senator' persona. Which is apparently also the same vocal style that he uses in the original trilogy, after he's shed his friendly senator persona.

Does the shift in vocal style in this case indicate that Sidious is using the Force to help him convince Anakin to slay Dooku, so as to help turn Anakin to the dark side?

Or does it just mean he's ready to start revealing his Sidious persona to Anakin and he's becoming impatient?