A multi-channel recording is recording more than two channels of audio on the same computer simultaneously. It requires specific drivers, hardware, and recording software for the platform you’re using, for instance, Windows 10, macOS, or Linux.
Most audio you hear is in stereo, but you can get your computer to mix sounds from different channels to mono so that you can play the combined sound through both speakers or in one speaker if you prefer, for example, if you have trouble with your hearing in one ear. Here’s a quick guide for what you’ll need to mix multi-channel input devices and down to mono.
To do multi-channel recording, you’ll need a sound card or external audio interface with sufficient Analog to Digital Converters (ADCs). You might have to replace your sound card if it has only one pair of stereo ADCs to switch between when recording different audio inputs.
Your drivers might be a problem because most computer sound interfaces were designed before multi-channel recording was possible. Your driver must allow you to record more than two channels simultaneously, so you might need a new one.
The application you record with must be able to support recording multiple channels of audio.
Successive Windows versions came out with different sound interfaces:
Windows MME (Multi-Media Extensions) came with Windows 3.1. But it’s not suitable for multi-channel recording.
DirectSound was introduced after Windows 95. It allows multi-channel recording on some devices.
ASIO was introduced by Steinberg to improve audio playback. It bypassed MME, but only one application can use its audio interface at a time.
WASAPI application programming interface (API) was introduced with Windows Vista. It allows a few multi-channel devices to work. But direct hardware access is limited.
How to multi-mix input channels on different platforms
Windows 10 can mix multi-channel inputs to mono. You can play everything combined through both speakers or use one earbud. The mono audio option is built into Windows 10 settings.
To find this option, click the Start button and select Settings. Then, click Ease of Access in Settings.
Click Other options in the sidebar. On newer versions of Windows 10, select Audio under Hearing in the sidebar. Scroll down, and you’ll find Mono audio under Audio options. Turn it On. Turn it off if you want to disable this and go back to standard stereo audio.
Windows 7 and 8
Older versions of Windows, including Windows 7 and 8, can’t mix both stereo tracks to mono without third-party software. You can use VoiceMeeter free on any Windows version.
macOS is standardized on the Core Audio sound interface.
Another way to do multi-channel recordings is to set up an Aggregate Device. It will allow you to use audio inputs and outputs from different devices simultaneously with Logic Pro, GarageBand, MainStage, and other Core Audio-compliant applications. An Aggregate Device combines inputs and outputs from multiple devices, so they appear as a single device in an app. One way to set it up is with Soundflower, Audio MIDI, and Audacity.
Go to System Preferences -> Sound
You can use the internal mic as your input and headphones as your output to record.
Click the menu bar, and choose Audio Setup from the popup menu. You’ll need a DAW (Digital Audio Workstation) application for multi-channel recording. We installed Ardour. Download and open it.
You will then see the Audio MIDI setup application. From here, create an Aggregate Device by clicking on the + icon on the bottom left.
Set your input as your Aggregate Device, and pass that as output to Soundflower (2 Ch).
Start Audacity and select Soundflower as the input. This should move your audio inputs into Audacity, where you can funnel multi-channel audio to mono.
Most new development for Linux uses ALSA as a sound interface rather than the older OSS. You can also do a multi-channel recording with a DAW (Digital Audio Workstation) application like Ardour in Linux Mint. You must connect your miniDSP device via USB.
To start Ardour, find it in Sound & Video in the main menu (your version of Linux may differ). When Ardour starts, set the following parameters.
On the next screen, type 8 for Create Tracks and click OK. Press the record and play buttons. Ardour will record all 8 input channels. Mix and export it in mono.
Multi-channel to mono on computers
Recording multi-channel audio and outputting it as mono is not impossible on your computers running on different operating systems without using external devices. There’s always more than one way to do anything, and a bit of research and experimentation will show you the best approach to suit your equipment and preferences.