How to use two audio outputs at the same time on a Mac, per app

The direct answer: a Mac can play through two outputs at the same time, but the native way — a Multi-Output Device in Audio MIDI Setup — mirrors the same audio to both devices. It does not send one app to one output and a different app to another. To use two outputs at once per app — say Spotify on the desk speakers while a call stays in your headset — you need per-app output routing: point each app at its own device. You can rig it for free with an app's built-in output picker or with BlackHole, or set it as one rule in a routing app and forget about it.

There are two very different questions hiding behind "use two outputs at once," and macOS answers only one of them out of the box. If you want the same sound coming out of two devices — laptop speakers plus a Bluetooth speaker in the next room, for a party — the built-in tools handle it. If you want different apps on different devices at the same moment — the thing most people actually mean — that's per-app routing, and it lives in third-party territory. This guide separates the two so you don't spend an hour building the wrong setup.

What "two outputs at once" really means on a Mac

macOS has exactly one active output device at a time. The Sound settings pane and the volume keys move that single device — everything the Mac plays goes there together. So the moment you want two devices making sound at once, you're already outside the plain Sound menu. The question is which of two setups you're after:

Mirroring — the identical audio out of two devices simultaneously. That's a Multi-Output Device, and macOS builds it for you. Per-app routing — this app to device A, that app to device B, both playing at the same time. macOS has no native control for it, even though Core Audio can address devices per app under the hood. Get clear on which one you need first; they use completely different tools.

The native path: a Multi-Output Device (and why it isn't per-app)

Open Audio MIDI Setup (in Applications → Utilities), click the + in the bottom-left, and choose Create Multi-Output Device. Tick the two outputs you want — say your built-in speakers and a USB interface — and set that Multi-Output Device as your system output. Now both devices play at once. It's free, it's built in, and for a "fill two rooms with the same music" job it's the right tool.

But read what it does carefully: it sends the same stream to every device on the list. Every app on your Mac plays through both outputs identically. There's no way to say "Spotify only on device A, the call only on device B" — a Multi-Output Device has no concept of which app is which. So if your goal is two different things on two outputs, this isn't it.

One honest catch: the master volume keys go greyed out when a Multi-Output Device is active — that's expected behavior, because macOS doesn't know which of the combined devices you mean to adjust. You end up setting each device's level individually inside Audio MIDI Setup. There's also an Aggregate Device, but that's built for combining audio interfaces (usually inputs for recording), not for the everyday "two speakers at once" job.

The free DIY path for per-app: the app's own output, or BlackHole

If what you actually want is two outputs carrying different apps, start with the cheapest thing that might already work. A handful of apps carry their own audio-output setting — VLC, some DAWs and media tools, and games with an audio-device option in preferences. If yours does, point it at one device and leave the system default on the other. Two outputs, two apps, at the same time, for free — that's a genuine, complete fix for that one app.

Most apps — Spotify, Chrome, Slack, most games, anything Electron — have no output picker at all. For those, the free route is BlackHole, a free, open-source virtual audio device, combined with Audio MIDI Setup. You install BlackHole (a one-line Homebrew install or a signed installer), route the app into the virtual device, then build an aggregate or multi-output chain that lands it on the real hardware you want. It genuinely works, and audio tinkerers rely on it. This is the same DIY toolkit covered in the companion guide on sending an app's audio to a different output on Mac.

The honest catch: it's setup-heavy for this specific goal. BlackHole is designed to pass audio between apps and duplicate a stream across outputs, not to hand you a simple "this app here, that app there" switch. Getting exactly two apps onto two devices at once usually means each app still needs its own output picker anyway, or a stack of aggregate devices you maintain. Great if you enjoy the tinkering; a lot of moving parts if you just want the split to hold.

The gotcha worth knowing: Background Music is volume, not output

Background Music comes up constantly as the free per-app answer, and it's excellent at what it does — but it does volume, not per-app output. As of 2026 it keeps every app on the same system output device; assigning one app to a different output is a long-standing open feature request, not a shipping capability. So for "run two outputs with different apps on each," Background Music can set the levels but can't do the actual routing. Worth knowing before you install it expecting it to split your outputs.

The set-it-once path: a per-app routing app

A per-app routing app does at the OS level what these apps won't do themselves: it assigns each app an output device independent of the system default. You set the default output to device A, add one rule for the app you want on device B, and both play at once — different apps, different outputs, no mirroring. It persists across restarts and reconnects, so the setup holds without you reopening Audio MIDI Setup.

SoundSource from Rogue Amoeba is the deep option here: it sends individual apps to different outputs, adds effects and EQ per app, and version 6 added grouped output devices and AirPlay streaming. It's a one-time $49. Fader does the same per-app output routing in a clean list — set a device per app and it sticks — for a one-time $19.99, and it also rides per-app volume straight from your keyboard, so you can balance the two outputs' apps against each other without hunting through menus. Here's how the options line up for running two outputs at once, per app.

The exact setup: two apps, two outputs, at the same time

With a per-app routing app the recipe is three steps:

1. Set the default system output to device A (say your desk speakers) — that's where everything plays unless told otherwise. 2. Add one app route: pick the app you want on device B (the call, the game, the video) and choose that second device as its output. 3. Leave it. The routed app lands on device B, every other app stays on device A, and both play at once. Add a second route and you've got three apps across two outputs — the tool doesn't care how many rules you stack.

In Fader that's the Routing tab: the default output sits at the top, and each app route is a row — App → Device — from a dropdown. Because the same app also gives every running app a fader on your keyboard, you can nudge the level of whatever's on either output with letter keys without touching the Sound menu. If your real need is the narrower "one app in the headphones, everything else out loud" version of this, the focused walkthrough on sending one app to headphones while the rest stays on speakers covers exactly that split.

Bottom line

A Mac can absolutely run two outputs at the same time — the question is what you want on them. For the same audio out of two devices, a free Multi-Output Device in Audio MIDI Setup is the right tool, greyed volume keys and all. For different apps on two outputs at once, that's per-app routing: free if your app has its own output picker, capable-but-fiddly with BlackHole, and off the table for Background Music, which only does volume. If you'd rather set one rule and move on — this app on the speakers, that one on the headset, both playing — a per-app routing app is the straight path. SoundSource is the deep, $49 option; Fader does the routing plus keyboard-fast per-app volume for $19.99 one-time.