AV Voice Changer can do some stuff you want. You can get a trial- or sharewareversion on the internet. Beware of some sites that offer you an "installer download" that will download the programm later. You dont want to get involved with bad stuff on you computer, right?

I used that program some time ago. Its not very good. I used around half a dozen of those tools in the past, none of them was really worth remembering. If you find a good one, let us know. I ask myself, what professionals use, unfortunately there is very few information about that on the net.