I have a challenging task
Task:
Just say something into your iPhone or capture a friend saying something. Then application make it sound even MORE ridiculous with your choice of over a dozen different voices. Voices of animals, guitar, drum etc. In this task we have to convert Pitch Manipulation I suppose.
The easiest way to change the pitch would be to speed it up or slow it down (half speed = down one octave, 2x speed = up one octave). But there are algorithms for maintaining speed...
http://www.dspdimension.com/admin/time-pitch-overview/
http://users.ecel.ufl.edu/~cdeng/pitch_shifting_algorithm.htm