In a discussion on using OSC to communicate over networks, Darryl just mentioned that OS X (apparently starting from Tiger) has the possibility to send MIDI messages over the network. I wonder how I have managed to oversee this feature, since it is sitting there as an option right in the Audio MIDI setup. The help file reads:
You can use the MIDI network driver to send and receive MIDI information between computers over a network. For example, if you have a music studio with several computers connected to MIDI interfaces, keyboards, synthesizers and such, you can use the MIDI network driver to route the data from these devices to and from your computers over an Ethernet network. Normally, you might need to purchase MIDI interfaces for your devices and connect the devices with cables. With the MIDI network driver, you can have a central computer act as a “master” sending and receiving MIDI data over the network to other computers and their connected MIDI devices.
To set up MIDI networking on your computer, you first create a “session.” A session identifies your computer as a central location for MIDI streaming over the network. From a directory of computers on your network, you choose the computers you want to participate in the session. You can also add addresses of computers not on your local network. Once identified, these computers in the directory can send and receive MIDI information from your computer and its MIDI devices. Each computer listed in the directory becomes a “participant” in the session.
When setting up a session on your computer, you specify the computer port that the network information will use, a session name, and your computer’s name that will appear to other computers on the network. You can also set up specific routings of MIDI devices. For example, you might specify that a MIDI keyboard connected to another computer route its MIDI data to a synthesizer connected to your computer.
The best thing is that it actually works!