I'm quite excited but can't test this yet (just moved and haven't unpacked or set up my rig!) A new Audio Units plug in called "midiO" (that's midi-Oh, not -zero) is available at Version Tracker. And yes, it's FREEWARE! From the Read me file: ============== Introduction MidiO is a small Audio Unit that can be used to drive MIDI based devices with the notes from a software instrument track within GarageBand. In its current form, it is not intended to be a general purpose, full functionality MIDI interface. What it does do is send the MIDI notes and other messages from a software instrument track to some other MIDI enabled program or device. It does not support the direct export of a MIDI track to a file. Usage Start up GarageBand. Double click the MIDI (software instrument) track that you want to send MIDI notes from. Click the details triangle and choose "Midi Out" as the generator. By default, the MIDI messages for the selected track will be routed out to a MIDI port labeled midiO on channel 1. If you wish to drive an external device or send messages to a different channel, select the midiO options button (the "pencil" icon button) and use the appropriate pulldown to select either the MIDI destination or channel. Now, when one plays the GarageBand song, all MIDI notes and messages for the selected track will be sent to the selected MIDI destination. In addition to selecting a track for midiO to ouput to, insure that the track selected for MIDI in (a software track highlighted to light green) is not set to a track that midiO is driving. There is no way (at least that I know of) of telling GarageBand to ignore certain MIDI sources. Thus, if one selects a midiO track as a MIDI in track, a dreaded MIDI loop in which the same notes are repeatedly rendered will be created. If you do create such a loop, you may hear a weird buzz or hum, or GarageBand might slow to a crawl. To clear a MIDI loop, stop playback, choose a different GarageBand track for input, and start again. CAVEATS MidiO does not playback MIDI sysex messages. If this is important to you, let me know. It should be relatively easy to add. Has only been tested under Panther. I've successfully driven Reason via re-wire and an external keyboard. I have observed dropped notes when sending messages to my cheap Casio keyboard. Let me know if you see this problem also or whether it's just a problem with my keyboard.