Abbreviation for Inter Application Communication or Channel, depending upon whom you talk to. Either way the purpose is the same. IAC is a Mac driver that was developed years ago and included as part of OMS to provide a way to link timing and other information between two different programs running on the same computer. It has most commonly been used to link a MIDI sequencing program and an audio recording program together to so they run in sync on one computer. It does this by providing a selectable software conduit for MTC, MIDI Clock, or other timing and location information to pass between the two pieces of software. Once enabled timing and location information can be sent from one program to another causing them to locate, start, and play in sync.