- set you mac volume to about 3/4
- connect audio in and out on your mac together with a cable
- get an audio track ready to record in metro
- find the itunes track you want........start it playing
- hit record in metro
- stop recording when itunes finishes
- go into metro and select silent areas in the graphic window's audio track and select 'delete time' from the edit menu
You can zoom down to a high magification and get the end and start points of the audio so exact that you don't even hear a click between them.

Scoot.