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 configuration

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 talking

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

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 processes

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 channels

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.

You can monitor outputs, too, which is useful when you’re
plugging them into places that aren’t playing the results as
well, or where you want to listen to a combined set of audio
without routing it to a program. You could pipe simultaneous
calls you linked together, as in one of the above examples, and
then use a monitor to listen to them all on a headphone output.

The graphical approach in version 2 lets you drag output
connections almost like you’re grabbing audio cables and
plugging them into different jacks. This can get a little
tricky in three ways before you get fully used to it. First,
you always drag a new wire from the output channel “jack” of a
source to an output channel, or from an output channel to a
monitor. You cannot drag to move the link from an
input side, which seems like a logical and intuitive
action—except it isn’t supported.

Second, you can route an output to multiple inputs, dragging
repeatedly from the same output jack. But dragging a new “wire”
doesn’t re-reroute existing connections, even though that might
also seem logical. Third, to avoid accidental deletion of audio
routing, when you select a route and it highlights by
thickening its line, pressing Delete on its own doesn’t remove
it. Instead, you have to use Command-Delete.

Loopback pairs neatly with two other Rogue Amoeba products:
Audio Hijack Pro ($59), which has a few feature
overlaps, and Farrago ($49), a soundboard that lets you
store and play sound effects and audio snippets. Audio Hijack
Pro includes recording and effect options, and is aimed more at
a front-to-back audio-capture process. Loopback makes it easier
to create and control sets of devices to feed into Audio Hijack
Pro, however, and make them available systemwide. Farrago can
be just another sound source into a Loopback interface. Rogue
Amoeba has two bundles that reduce the cost: Loopback and Audio
Hijack Pro for $130 and those two apps plus Farrago and its
Fission simple audio editor for $175.

Bottom line

Loopback 2 offers significant improvements over the initial
release across the board, even though version 1 was quite
useful and good. The interface change to allow a more visual
drag-and-drop approach helps considerably, as does exposing
Pass-Thru as yet another element in sources. The addition of
volumes controls for setting balance is completely invaluable.

Apple didn’t include robust audio routing and mixing controls
in macOS, and it’s hard to blame the company for that, because
only a small subset of Mac users need them. Loopback bridges
that gap, although its $99 price tag aims the product at audio
professionals, podcasters with a budget, or business users.
It’s not a casual tool, but it can be vital and affordable for
those for whom this review left them pumping their fists.

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