If you have an early 2009 Mac Pro running Mac OS X 10.6.2, and are experiencing extraordinarily high processor utilization when working with audio (playing or recording music), be sure to apply Apple’s recent Mac Pro Audio Update 1.0.  This update installs a new AudioAUCC kernel extension, which reduces CPU usage when processing audio.  It has also been rumored that this updated can be applied to other Mac models that are experiencing similar issues.