Far from being an expert, I'm just an amateur musician trying to learn to play the guitar with GarageBand. Initially, I plugged my electric guitar directly to my Mac Pro with the audio line-in input. It does work, but the sound is squashed and not very musical. With the M-Audio Fast Track, I just connect the guitar to the audio interface plugged to one the computer's USB ports. On the Mac, all you have to do is remember to select the Fast Track input 2 as your sound input for the guitar in GarageBand. No drivers or software to install. It just works and the sound is really good now. A worthy investment.