iTunes 4: Effects Can Cause Some Sound Fluctuation During Playback

Update to a later version of iTunes 4 if you hear a rapid fluctuation in volume in iTunes 4.0.
Symptom

When playing a song, the sound volume fluctuates rapidly, or you hear other distortions.

Solution

Download and install iTunes 4.0.1 or later. It is available from the Software Update pane in System Preferences, or from the iTunes website (http://www.apple.com/itunes/download/).
Published Date: Feb 18, 2012