SoundTouch is an open-source audio processing library for changing the Tempo,
Pitch and Playback Rates of audio streams or files.

The SoundTouch library is suited for application developers writing sound
processing tools that require tempo/pitch control functionality, or just for
playing around with the sound effects.

The SoundTouch library source kit includes also an example utility SoundStretch
that allows processing .wav audio files with command-line interface.