Any Mac app recommended for audio editing?

I would like to have a mac software performing the following functions:
-fully accessible with voiceover
- can alter the speed of a audio track, say if speed increase, the voice will become high pitched like a little girl and if the speed decreased , will become like a old old men and is very low in pitch (similar function is found in goldwave of Windows)
- can have a voice changing effect, making your voice recording changing from a male voice to a female or a cartoon voice etc
- the edited one can be exported into audion files

Of course a free one is preferable, but if a paid one can perform all the above functions, I will consider, Many thanks.