IAC Inter-Application Communication
The IAC
(Inter-application communication) Driver in Mac OS allows you to
create virtual MIDI cables between applications inside the box, so
to speak. This lets you share midi information without the
restrictions of Rewire!
1) Open Audio Midi
Setup (APPLICATIONS > UTILITIES > AUDIO MIDI SETUP)
2) Open the MIDI
window
• in OS 10.5,
click on the "MIDI" tab
• in OS 10.6
(Snow Leopard), go to WINDOW > MIDI WINDOW
3) Once there, you
should see something like this:
4) Double click on
"IAC Driver" to open it, then you should see something like
this:
(if you only
see some of it, try clicking on the little arrow next to "More
information")
5) To use the IAC
Driver, first you must TURN IT ON! Click on the "device is
online" checkbox
6) In the
"Ports" list, each one of those is a virtual MIDI cable,
through which you have 16 channels to send MIDI! It's
helpful to rename these so you know what they are when
you're choosing them in your DAWs. (To rename, double-click
on the port and enter a new name)
7) In a DAW,
like Logic, "IAC Bus 1" (or whatever you named it) will be
an option as a MIDI input and MIDI output (as if you plugged
in a new MIDI interface). To send MIDI from an "External
MIDI" track to somewhere else, choose the "IAC Bus 1" as a
port in the Inspector
Looking at the image above, that means any MIDI
played (or read) on the "Grand Piano" external midi
track is going to be sent out the IAC Bus 1 on
channel 1.
8) In
another application (in this case, let's use Plogue)
the IAC Bus 1 will also show up as an input and
output MIDI device
-
To use it, create a new "MIDI device" module -
you'll want "Input" if you want MIDI from Logic's
external midi track to trigger sounds in Plogue
9)
Now you've got a module/bidule that
is receiving midi from IAC Bus 1 (in this case,
from the "Grand Piano" external midi track in
Logic)
-
The bidule below is outputting all 16 channels
through one plug:
- If we want to route the MIDI channels
separately, just add a "midi splitter" - this
will divide the MIDI signal into 16 discrete
channels, which you can then route to plugins,
etc
10) In the setup below, we're sending MIDI
from the "Grand Piano" external midi track is
sending MIDI through channel 1 on the "IAC Bus
1" - that bus is routed to Plogue, where the
signal is divided into 16 discrete MIDI
channels - channel 1 is routed to an audio
unit instrument called "Chip 32" (a great
chiptune/video game sound instrument), which
is then routed to output 1 and 2 of the main
audio interface.
Notice the change of TYPE of cable! It's
MIDI when it comes out of the IAC Driver,
and MIDI after it's split into 16 channels,
but once it goes "through" the Chip32
instrument, it becomes audio, and can then
be routed like normal audio.