How to Maximize Your Inputs with Aggregate Audio
Your Mac’s built-in audio hardware lets you record a single stereo track or two mono tracks simultaneously. If you create music one part at a time via overdubs, that may be all you need.
But what if you want to record a stereo keyboard and a vocal at the same time, for a total of three tracks? Or two stereo guitars (four tracks)? Or an entire band (lots of tracks)?
It’s easy to do this with a third-party digital audio interface that connects to your computer via a USB or FireWire cable. And thanks to your Mac’s Aggregate Audio feature, you can maximize your input track count by recording through several such devices simultaneously. This tutorial shows you how.
Building an Aggregate Audio Device
No matter which interfaces you use, the setup procedures are similar.
As an example, imagine two guitarists who want to record themselves jamming together to backing tracks in GarageBand or Logic Pro. One player owns a Line 6 PODxt, a popular interface with built-in guitar effects. The other has an M-Audio Black Box, another popular interface with onboard effects.
Step 1: Visit the interface manufacturers’ websites to verify that you have the latest driver software.
Step 2: Connect the interfaces to your computer.
Step 3: Open the Utilities folder inside your Applications folder. Double-click on Audio MIDI Setup.
Step 4: Click on the Audio Devices tab.
Step 5: From the Audio Menu, select Open Aggregate Device Editor.
Step 6: Click the + sign to create a new Aggregate Device. All connected interfaces should appear in the Structure Window.
Step 7: Select the ones you want to use (in this case, PODxt and M-Audio Black Box).
Step 8: Click “Done” to close the editor and return to the Audio MIDI Setup screen.
Step 9: Select “Aggregate Device” as your Default Input. Don’t change your output setting.
Step 10: Quit Audio MIDI Setup. Your Aggregate Device will now appear in any Audio Unit-compatible application.
Note the order of your devices. The device names do not appear in your audio software — only the words Channel 1 & 2, Channel 3 & 4, and so on. Just remember that the devices appear in the order in which you activated them in the Aggregate Device Editor. In this example, we enabled the PODxt first, so its output appears on Channel 1 & 2. The Black Box, which has four output channels, is on Channel 3 & 4 and Channel 5 & 6. Had we enabled the Black Box first, it would appear on Channel 1 & 2 and Channel 3 & 4, and the PODxt would be on Channel 5 & 6.
Next: Recording Your Aggregate Audio Device in GarageBand or Logic Pro
