Guides / Virtual audio drivers and Audio MIDI Setup

How to create an aggregate device on a Mac

Tested on macOS 26.4.1 (Tahoe), Apple M3 Max, 3 Sept 2026. Updated 2026-09-03.

An aggregate device is one Core Audio device built from several. You create it in Audio MIDI Setup: click the Add (plus) button, choose Create Aggregate Device, tick the Use box for each device, pick one Clock Source, and set every device to the same sample rate (48 kHz is typical). Enable Drift Correction on every device except the clock. Apple's example merges an 8-channel and a 2-channel interface into one 10-channel device.

How do you create an aggregate device on a Mac?

Steps per Apple's guide, checked on macOS 26.4.1.

1. Open Audio MIDI Setup (Command-Space, type Audio MIDI). If you only see MIDI Studio, choose Window > Show Audio Devices.
2. Click the Add (plus) button at the bottom of the sidebar and choose Create Aggregate Device. A new entry appears in the sidebar.
3. Click the name once to rename it.
4. On the right, tick the Use checkbox for every device you want inside it. The order you tick them is the channel order the aggregate exposes.
5. Open the Clock Source pop-up and choose the device with the most reliable clock. A USB interface is a better clock than a built-in mic or a virtual driver.
6. Set the Sample Rate so every member matches the clock source, 48 kHz if in doubt.
7. Tick Drift Correction for every device that is not the clock source.
8. Pick the aggregate as the input inside your DAW or recorder, or Control-click it and choose Use This Device for Sound Input.

To remove it later, select it in the sidebar and click the Remove (minus) button. Removing it does not uninstall any driver that was part of it; see uninstalling BlackHole or Soundflower for that.

Which device should be the clock source, and what does drift correction do?

Every audio device runs on its own crystal, so two devices set to 48 kHz never agree exactly, and over an hour the difference becomes clicks, dropouts, or a drifting stereo image. Apple's Set aggregate device settings page describes drift correction as resampling that keeps devices in sync when they have no hardware synchronization, and it gives three rules:

• No hardware sync between the devices (the normal case: a USB interface plus a USB mic, or a mic plus BlackHole): choose the device with the most reliable clock as Clock Source and enable Drift Correction on all the others.
• Some devices share a hardware clock (word clock or ADAT): choose that hardware chain's primary as Clock Source and enable Drift Correction only on the devices outside the chain.
• All devices share hardware sync: leave every Drift Correction box unticked.

The clock source also fixes the sample rate. Apple's guide is explicit that all devices in an aggregate must run at the rate of the clock source. If one member only supports 44.1 kHz, the whole aggregate has to run at 44.1 kHz, even if your interface would rather run at 48 kHz. Check each member's Format before you build the aggregate; a mismatch is the usual reason one member records silence.

When do you actually need an aggregate device?

You need one when a single app must read from two physical or virtual devices at the same time. Real cases:

• Two interfaces in one DAW. Apple's own example: an 8-channel interface plus a 2-channel interface become one 10-channel device, so Logic or Ableton sees all inputs.
• A USB mic plus an interface. Vocal on a USB mic, guitar on the interface, both into one session.
• Your mic plus a virtual driver. To record your voice and the Mac's playback into one multitrack file, people aggregate the built-in mic with BlackHole. That works, but it also means building a multi-output device so you can still hear anything. The simpler route for that job is described in recording computer audio and microphone at the same time.

You do not need one for a single interface, even a multi-channel one: a Focusrite Scarlett 8i6 already exposes all its inputs as one device, and a recorder with a channel picker takes the pair you want. You also do not need one to record what the Mac plays; that is a ScreenCaptureKit job.

Why does my aggregate device click, pop, or drift out of sync?

Three causes cover nearly every report, in this order:

1. Drift Correction is off on a non-clock device. The BlackHole wiki puts it plainly: clock synchronization issues between devices can cause clicks, pops, or audio drift over time. Tick the box for every device except the Clock Source.
2. Sample rates do not match. The wiki's other warning: devices running at different sample rates may fail to work correctly together. Select each member in the sidebar and set its Format to the same rate, then reselect the aggregate.
3. The clock source is the weakest device. If BlackHole or a Bluetooth headset is the clock, everything else resamples against a software clock. Make the hardware interface the clock.

A fourth cause is a member being unplugged: Core Audio assigns a new device ID on reconnect and a running recording usually stops. An aggregate has no watchdog for that, so for long unattended captures a single device is safer.

Does an aggregate device mix the sources into one stereo track?

No. An aggregate exposes all channels of all members side by side; it does not sum them. The BlackHole wiki states that aggregates expose all channels from all included devices, so the recording app must be told how many channels to capture. A built-in mic (1 channel) plus BlackHole 2ch (2 channels) is a 3-channel device. Record it in a stereo recorder and you get channels 1 and 2 only: the mic and the left half of the playback. Record it as three separate tracks in a DAW or in Audacity with the channel count set to 3 and you get everything, but still as separate tracks that you mix afterwards.

If you want one finished stereo file with voice and playback blended, an aggregate is the wrong tool. Loopback ($99) or Audio Hijack ($69) mix before recording; AirCheck does not mix either. The Loopback vs BlackHole vs no driver comparison shows which tool mixes and which only routes.

Combining or picking audio sources on a Mac: which tool does what (checked 3 Sept 2026)

Loopback price from rogueamoeba.com/loopback/buy.php on 3 Sept 2026. Loopback needs macOS 14.5 or newer.

Where AirCheck fits

AirCheck ($39, macOS 14 or newer) is for the case where you do not need an aggregate at all: one interface, one mic, or the Mac's own playback. On a multi-channel interface it shows a channel-pair picker (Ch 1-2, Ch 3-4, and so on, or all channels), so a DJ mixer wired into inputs 3 and 4 of a Scarlett 8i6 is recorded without touching Audio MIDI Setup. It records 24-bit at the device's own rate and exports WAV or MP3.

When you do not need it: If you need two devices in one DAW session, or mic plus playback in one multitrack take, build the aggregate; that is a free Audio MIDI Setup feature and AirCheck does not replace it.

Questions people ask

How do you aggregate an audio device on a Mac?

In Audio MIDI Setup click the plus button, choose Create Aggregate Device, tick Use for each device, set one Clock Source, match the sample rate on every member, and tick Drift Correction on the non-clock devices. Then select the aggregate as the input in your app.

Can an aggregate device include BlackHole?

Yes. Tick BlackHole 2ch and your microphone. Make the microphone or interface the Clock Source and enable Drift Correction on BlackHole, as the BlackHole wiki recommends. You still need a Multi-Output Device to hear the playback while it is routed into BlackHole.

Why does my aggregate device have no sound on one input?

Usually a sample-rate mismatch: one member is at 44.1 kHz while the clock source is at 48 kHz. Set every member's Format to the same rate in Audio MIDI Setup. The second cause is a channel count set too low in the recording app.

Does an aggregate device add latency?

Drift Correction resamples the non-clock devices, which adds a small amount of processing. Apple does not publish a figure and this page does not invent one. For tracking with headphones through the interface's direct monitoring, the aggregate's latency does not matter.

Sources

• Apple: Combine audio devices into a single aggregate device
• Apple: Set aggregate device settings (Clock Source, Drift Correction)
• Existential Audio: Aggregate Device (In Depth) wiki
• Rogue Amoeba: Loopback purchase page
• Rogue Amoeba: Loopback (system requirements)

Related guides

• How to create a Multi-Output Device on a Mac (and keep hearing your audio)
• What is Audio MIDI Setup on a Mac?
• Loopback vs BlackHole vs no driver for recording Mac audio
• Is BlackHole safe for a Mac?
• Is Soundflower safe, and does it still work on a Mac?
• How to uninstall BlackHole or Soundflower on a Mac
• Virtual audio drivers and Audio MIDI Setup: all guides
• Every guide, by topic