Time-scaling of audio aims to modify the duration of an audio signal without changing the instantaneous frequency content. This cannot be achieved simply by changing the sampling rate since that would alter the frequency content as well. Pitch-shifting is a sister modification, that aims to shift the pitch of the signal by some amount without changing its duration. The two operations are closely related in the sense that if one of them can be carried out successfully, then the other can be obtained easily by a rate changer. The aim of this project is to implement methods to realize these two tasks, possibly on an iPhone.