Best/Easiest way to send MIDI data from arduino to garageband

Keith thanks for the suggestion but I'd rather not have to mess with the firmware.

dxwood I've tried that but I can't seem to get it to work. When I choose the MIDI baud rate (31250), it won't let me choose an output port, but I can select it for any other baud rate. And sometimes the Serial RX square at the bottom blinks red depending on which baud rate is selected. Also, how can I tell if garageband detects the device. Will it automatically start making noises when I open it?

Any help is greatly appreciated. Thanks!