What is it?
Rewind lets you rewind at speeds up to 32 times faster or slower.

How to use it
If you select Rewind from the menu, it will "lock" rewind on.  If you select Rewind with Command-"<", it will rewind as long as you hold the key down.  Hold down the option key for slow motion.  You can use Rewind whether a sound is playing or not.  If a sound is not playing and no part of the sound is selected, the cursor will be left at the point rewinding stops.  The Rewind speed is set in the "Sound Out" Preferences.

Notes  
See "Sound Out" Preferences for more information.