Rubber Band Library 1.4

Rubber Band Library is a high quality software library for audio time-stretching and pitch-shifting. It permits you to change the tempo and pitch of an audio stream or recording dynamically and independently of one another.

Rubber Band Library is intended for use by developers creating their own application programs rather than directly by end users, although it does also include a simple (free) command-line utility program that you can use for fixed adjustments to the speed and pitch of existing audio files.