Loopback 2 review: Elevates the interface for sophisticated sound routing in macOS

If you’ve ever used a app that accepts an audio input and was frustrated that you can specify only one piece of audio hardware, or if you’ve wanted to route the sound output of an app into a Skype, FaceTime, Google Hangouts, or other conversation, Rogue Amoeba’s Loopback is the program you need. The latest version improves significantly on its predecessor, which itself was quite powerful.

loopback2 typical configurationIDG

A typical configuration lets you route the output of multiple apps into a single device that you could use to record or pass to another app.

The app lets you combine hardware audio—like mics and line input—with the audio output of apps and system-level components, like Text-to-Speech, to create virtual audio devices. A combined audio device appears as a single item you can select as an input in programs like GarageBand or Skype. You can also select it as an output device, too, playing into the virtual audio equipment system audio or the sound out of apps that allow audio output selection.

Version 2 simplifies the previous interface, making it easier to connect audio sources and providing you a better view of how you’ve configured a virtual audio device at a glance. It also adds volume controls for every component in an audio workflow, which lets you really mix the sound together instead of have to control it from the source—often not a possibility—or dealing with out-of-balance levels.

loopback2 look how siris talkingIDG

You can even capture Siri talking.

Loopback can be used in both extremely simple and complicated ways, and it benefits from practical examples. Here are a few.

  • Taking the output of a tab in Safari that’s playing cable channel news and recording it through QuickTime player.
  • With multiple USB mics attached, combining their input to feed into a FaceTime call.
  • Managing a call with people across multiple internet audio apps, like audio calls within Slack and Google Hangouts, so that you and everyone can hear each other.
  • On a podcast with remote guests, where you want to have background music, live music, or snippets play during the recording that everyone on the connection can hear just as you can.

That scratches the surface. But if none of these uses remind you of tasks you’ve tried to manage or want to do, Loopback likely doesn’t meet your interests.

One step shy of literally “plug and play”

Setting up Loopback is a simple matter, made more visual and easier to understand in version 2. You click a + to create a new virtual device, then select sources. A drop-down menu shows all running apps and connected audio input devices. Hold down the Option key and a Running Processes menu item appears, letting you select the audio output of anything currently running in the foreground as an app or in the background as a system process or agent—this includes Siri and other parts of macOS that produces audio or “speaks.”

loopback2 capture running processesIDG

An Option-click gains access to everything running on a Mac, including hidden agents.

Every new device automatically includes Pass-Thru, which lets it be used as an audio input as well as a combined output, useful for apps that let you choose a specific audio output device. For example, you might want to dump the output from an audio editor program as the input of a Skype call, so someone else could listen to changes and approve them as you edit.

loopback2 many many channelsIDG

I’m sure some folks need this many channels, and if so, Loopback is there for them.

Loopback 2 supports up to 64 channels of passthrough audio, letting you take up to 64 input channels (32 stereo channels) and pipe to any combination of up to 64 output channels. That is a heck of a lot. The previous limit was already quite high at 32, and clearly some users asked for more. With large recording projects using a lot of mics or other sources, Loopback could allow a producer or mixer to bypass more expensive software.