wav is a dead-simple API for dealing with WAV audio files.

I have created many examples in the form of command line utilities. These utilities are as follows:

• wav-crop - cut a WAV file
• wav-duration - get the duration of a WAV file
• wav-gradient - fade in/out a WAV file
• wav-overlay - play one WAV file on top of another one
• wav-tone - generate a sinusoidal tone at a given frequency
• wav-volume - change the volume of a WAV file

Full documentation is here