It's called Melodyne. It allows you to speed up/slow down each part of the voice audio file like you maneuver MIDI Notes o a sequencer.
From the website@ celemony.com :
"Melodyne is the perfect tool for pitch shifting and time stretching in convincingly natural sound quality, for correcting the intonation and timing of singing, for audio quantization, producing harmonies, and remixing and restructuring the melody, tempo or timing of existing recordings. With Melodyne you can actually do the impossible - and do it easily. "
