What is it?
Plays the sound in the active sound document.

How to use it
To play a loop, hold down the option key while selecting Play.

Notes
While playing sounds if the mouse doesn't move around smoothly or at all, try turning off the Mixer, Stereo, or Linear Interpolation.  If that doesn't work, try muting some of the tracks or Resampling to a lower sample rate.

See "Sound Out" Preferences for more information.