How to use two microphones at the same time on a Mac

macOS only lets one microphone be the system input at a time, so two people speaking into two separate mics for the same call or recording is not something it does out of the box. The fix is an Aggregate Device, built in Audio MIDI Setup, which combines several input devices into one entry an app can select. It gets both mics seen. It does not mix them into a single balanced signal for you.

This comes up in a specific set of situations: an interview with two guests on separate mics, a co-hosted podcast recorded locally rather than over a call, two presenters sharing one Mac for a stream, or someone who wants a lapel mic and a desk mic both live at once. In every case the instinct is the same: plug in a second microphone and expect the Mac to just use both. It won't, not without a step in between.

Why one microphone doesn't become two

System Settings, under Sound and Input, is built around picking a single winner. Select a microphone there and it becomes the one active input for the whole system; select a different one and the first stops being heard. There is no toggle for "use both," because as far as that screen is concerned, a Mac has one input at a time.

Audio MIDI Setup, a separate utility buried in Applications > Utilities, is where the actual mechanism lives. It can combine several real input devices into an Aggregate Device, which macOS then treats as one device with more channels than any single microphone has alone. An app that only understands "one selected input" can suddenly see channels from two or three physically separate microphones on that one entry.

Building the Aggregate Device

The setup itself takes a couple of minutes:

• Open Audio MIDI Setup (Applications > Utilities > Audio MIDI Setup).
• Click the plus button in the bottom-left corner of the device list and choose Create Aggregate Device.
• Tick the microphones you want combined, on the right-hand side of the window, under Use.
• Pick a clock source, usually whichever microphone you consider primary, and turn on Drift Correction for the others so the channels stay in sync over a long recording.
• Rename the device to something you'll recognise, then select it as the microphone inside whichever app you're using to call or record.

Once that's done, the app sees one input with all the ticked microphones' channels available on it, instead of two separate devices to choose between.

What an Aggregate Device does not do

This is the part that catches people out. Combining two microphones into one device makes both of them visible. It does not make them mixed. There is no balanced signal being created behind the scenes, no shared volume, and no automatic blend of both voices into a clean single track.

What actually happens depends on the app. Most calling and recording software is written to listen to one microphone, so once it sees an Aggregate Device it will pick up whichever channel, or pair of channels, it is configured to use, often just the first one. The second microphone can be sitting right there on the same device and still not be heard, unless the app specifically supports multi-channel input and lets you assign which channel is which speaker. Some do. Plenty don't.

Independent level control per microphone, so one voice doesn't drown out the other, is a further step this doesn't cover at all. Getting a genuinely mixed, balanced signal out of two microphones is really a job for actual hardware, a small USB audio interface with two or more inputs and its own gain knobs, or software built for it, recording each microphone to its own track in a DAW like Logic Pro or GarageBand and balancing them afterwards. An Aggregate Device is the step that makes two mics visible to one app. It was never meant to be the mixer.

Where Chorus fits, and where it doesn't

Worth being precise about this rather than overselling it: Chorus does not build Aggregate Devices, and does not combine microphones into one. Its grouping feature does the equivalent job on the output side, combining speakers into a Multi-Output Device, but inputs work differently in macOS and Chorus doesn't add anything to that side of the combining step.

What Chorus does do is list every input macOS can currently see, including an Aggregate Device you've already built in Audio MIDI Setup, in its own menu-bar panel, and let you switch the active one with a click or a keyboard shortcut. If your setup is a single mic you swap between a headset and a desk mic for different calls, that's a much faster path than System Settings; see our guide to choosing a microphone on a Mac for the rest of that. For running two mics into one app at once, Audio MIDI Setup's Aggregate Device is still the tool doing the actual combining.

For the step-by-step on building a Multi-Output Device, see Apple's own guide to Audio MIDI Setup.

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