How can I avoid Garageband's metronome to get recorded in an Audio Track?

Hi all,

My setup

Korg M50 (1/4 outputs connected to the 2x1/4" inputs on the back of the speakers, which have an Audio interface)

Macbook (GB)

Alesis M1Active 320 USB speakers with Audio interface. http://www.alesis.com/m1active320usb?tt=5

Workflow

I open a session in GB, create a new Real Instrument Track and setup input and output via the Alesis monitors, which have an Audio Interface and are connected via USB to the Macbook.

I turn the metronome ON, ie, I'm recording a bass line (Real instrument, not MIDI) and the metronome click is being recorded with the bass line. Turning off the Metronome is not an option because I need it to keep up with the tempo. Anyhow, if I was to record the bassline without the metronome and then, on a new instrument track I record a piano (Real instrument track), the piano gets recorded along with the bass line which resides on Track 1.

I've tried to use the Macbook Audio input (Same trial) and the speakers as an USB output, setup the recording levels on GB, metronome on or off and the metronome doesn't get recorded along with each track, so, it works.

Any help on this matter is appreciated.

Thank you.