How to Record Two Microphones at Once in GarageBand

You’ve got two microphones, one Mac, and GarageBand and GarageBand stubbornly insists on recognizing only one input at a time. Frustrating, but fixable.

The workaround is an Aggregate Device: a macOS-level trick that combines multiple audio inputs into a single virtual device that GarageBand is happy to use. It sounds more complicated than it is. The whole setup takes about five minutes, and once it’s done, both mics record to their own separate tracks simultaneously.

This guide covers the full process, from creating the aggregate device in Audio MIDI Setup to enabling simultaneous recording in GarageBand. Works on any Mac running a recent version of macOS.

What You’ll Need

• Two microphones connected to your Mac (USB mics, USB audio interfaces, or a combination)
• Audio MIDI Setup (built into macOS, no download needed)
• GarageBand (free from the App Store)
• Headphones for monitoring (more on why below)

One heads-up: if you’re using two identical USB microphones, same make and model, macOS may struggle to tell them apart since their device signatures are the same. Different mic models work more reliably. If you’re shopping for a second mic, keep that in mind.

Step 1: Create an Aggregate Device in Audio MIDI Setup

This is the key step. You’re telling macOS to treat two separate microphones as a single combined input device.

1. Open Audio MIDI Setup. The fastest way: press Cmd + Space to open Spotlight, type Audio MIDI Setup, and hit Return.
2. In the bottom-left corner of the Audio Devices window, click the + button.
3. Select Create Aggregate Device from the menu that appears.

4. A new entry called Aggregate Device appears in the left sidebar. Double-click it to rename it to something recognizable. “Both Mics” or “Podcast Setup” works fine.

5. With your aggregate device selected, you’ll see a list of available audio devices on the right. Check the box next to each microphone you want to include.
6. Note the order you select them, as this determines which mic becomes Input 1, Input 2, and so on. That order matters when you assign inputs to tracks in GarageBand.
7. If prompted to choose a Clock Source, select whichever microphone has the more reliable connection. For most setups, either works. Pick the one plugged directly into your Mac rather than through a hub.

8. Close Audio MIDI Setup. The aggregate device is now available system-wide.

Step 2: Set the Aggregate Device as Your Input in GarageBand

GarageBand needs to know to use your new combined device instead of a single mic.

1. Open GarageBand. If you’re starting a new project, go to File > New and choose your project type. In the new project dialog, click the arrow next to Details at the bottom left.
2. Click the Input Device dropdown and select your aggregate device from the list.

3. For Output Device, select your headphones. Don’t use Built-in Output, as routing audio back through your Mac’s speakers while recording can cause feedback and distortion in your tracks.
4. Click Choose.

If you’re working in an existing project, go to GarageBand > Settings > Audio (on older versions, this is GarageBand > Preferences > Audio/MIDI) and set the Input Device to your aggregate device there.

Step 3: Set Up Tracks and Enable Simultaneous Recording

This is where most people get stuck. Creating the aggregate device isn’t enough on its own. You need a separate track for each mic, with each track assigned to the correct input, and Record Enable turned on for all of them.

1. Create an Audio Track for each microphone. Go to Track > New Track and select Audio. Repeat so you have one track per mic.
2. For each track, click the track header to select it, then look at the Smart Controls panel at the bottom (press B to toggle it open). Under the Input section, assign the correct input number, Input 1 for your first mic and Input 2 for your second.

3. Now you need to add the Record Enable button to each track header. Right-click (or Control-click) on a track header and select Configure Track Header.
4. Enable the Record Enable option. Do this for both tracks.

5. You’ll now see a small dot in each track header. Click it on both tracks. It’ll blink red when active, indicating that track is armed for recording.
6. Press the main Record button (or R) to start recording. Both mics will record simultaneously to their own tracks.

Troubleshooting

Only one microphone is recording

The most common cause: Record Enable isn’t active on both tracks. Check that both track header dots are blinking red before you hit record. It’s easy to arm one track and forget the other.

The mics aren’t showing up in GarageBand at all

Go back to Audio MIDI Setup and confirm the aggregate device is still configured correctly with both mics checked. If you unplugged and replugged a mic after creating the device, you may need to re-check it in the device list.

One mic is much louder than the other

Input levels are set per-track in GarageBand’s Smart Controls. Select each track, open Smart Controls (B), and adjust the input gain independently. You can also check input levels in Audio MIDI Setup by selecting the aggregate device and watching the level meters.

Two identical USB mics aren’t being recognized separately

This is a known limitation. macOS identifies USB devices partly by their hardware signature, and two identical models can look like one device to the system. If you’re hitting this wall, the practical fix is to use different microphone models, or to run one mic through a USB audio interface to differentiate the inputs.

A Note on Audio Interfaces

If you’re recording podcasts or music regularly, a USB audio interface with two or more inputs (something like a Focusrite Scarlett 2i2) sidesteps this whole process. Both mics plug into the interface, which appears as a single multi-input device in GarageBand automatically, with no aggregate device needed. The aggregate device method works well, but it’s genuinely a workaround for a hardware limitation. An interface is the cleaner long-term solution if you’re doing this often.

That said, the aggregate device approach is free, it works reliably, and it gets the job done. For a podcast setup or occasional dual-mic recording, it’s a solid option, cautiously recommended with the caveat that identical USB mics can be a headache.