Computer Voice: Played straight with house brains and some institutional computers that talk to everyone around.  Played somewhat straight with muses, terminals, and various other more personal machines, with the twist that they’re talking to you inside your own head, on a secondary audio channel that doesn’t interfere with your ability to hear.  And can pick up your surface thoughts in reply, not just your subvocalization.  No-one wants to have the cellphone-conversation social problem made 10,000 times worse by people’s personal computing devices, after all.

And the voices, even the internal ones, are generally completely customizable to the user.  After all, when you have a constant companion inside your own head, you want to enjoy listening to them, right?