# Configuring Audio Sources

Virtual audio devices can be used as simple pass-thru devices, but Loopback provides much more power by allowing you to configure audio from specific sources to flow through a device. This is done by adding sources to the Audio Sources table.

The Audio Sources Table

To add a source to the table, click the + button to select an application or an audio device and have it added to the table. Any audio produced by the source will then be included in the virtual audio device’s output.

To remove an audio source, just highlight it in the table and click the “-” button, or press the Delete key on your keyboard.

Below, you can see that we've added the software applications QuickTime Player and iTunes to our device, as well as a USB Microphone.

The Audio Sources Table, With Sources Added

Thanks to Loopback, the audio from all these sources will be combined into one virtual device.

### Additional Settings

#### Muting Audio

With the “Mute audio sources” checkbox, you can toggle the muting of application audio sources included in the virtual audio device. By default, this checkbox is turned on. That means that when the virtual audio device is in use, audio from any sources included in the device will not be played through. This is usually desirable, as applications using the Loopback virtual audio device will frequently want to perform their own audio play-through, after some amount of processing.

The “Mute Audio Sources” checkbox should generally be left in its default On state. However, if you instead want the audio from sources to be audible regardless of how the application using the device is configured, you can toggle the checkbox off.

#### Monitoring Audio

With the “Monitor audio through” setting, you can direct audio from any audio sources to a secondary audio device. This can be useful for monitoring how your virtual Loopback device will sound to others. This setting is off by default, so if you wish to monitor audio, turn it on and select the desired output device.

Note that enabling monitoring will cause the Loopback virtual audio device to become active, even if no specific application is using the device. This will in turn cause the muting setting mentioned in the previous section to apply.

### Channel Mapping

By default, Loopback configures the channels for your virtual audio device automatically based on the sources you include. It will include as many channels as are needed to map channels from the audio sources one to one to output channels. Most users will likely want to leave the channel mapping in its default state.

If you wish to set a custom channel mapping, see the Manual Channel Mapping page for details.