hey... i am a first time mac owner and i have a question concerning Garageband 3. I am trying to record a real instrument track (guitar). I am using headphones and yet i am getting a ton of high pitched/whiny/screechy sound in the background. I try to control this by using the gate when recording, but as soon as i strum, i can still hear it in the background. I've played with all the volume settings (input & output) and i am at a loss! any help would be greatly appreciated.