Once you’ve got IAC (or windows equivalent) set up, you’ll need to open up Live’s preferences window, and head over to the MIDI/Sync tab. Under MIDI Ports, you’ll now see a virtual input and output port for the IAC driver.

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This means that you now have a new source and destination for MIDI data in Live. However, unlike standard MIDI ports which are used for communicating with hardware, the IAC ports are used for sending MIDI between applications on same computer.  For example, with IAC you could send MIDI out of a track…

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…and then into Logic Pro to control one of its built-in synths using Live clips.

There’s often no need to use this technique because there are many situations where ReWire handles inter-application MIDI automatically. The example above isn’t a candidate for ReWire, though because Logic doesn’t run as a ReWire slave. (You can use Logic to control Live’s built-in synths, but not the other way around.)

What we’re going to do is a little different. MIDI loopback involves sending data out of the IAC driver and back into Live. Why would we do such a thing? That’s up next…