Stereo recording can make audio feel wider and more immersive, helping listeners understand the space around a sound. Whether you’re capturing a live performance, recording environmental ambience or creating sound effects for video, the way microphones capture stereo information can make a significant difference.

One particularly flexible technique is mid-side recording, often abbreviated to M/S. Unlike some conventional stereo microphone arrangements, mid-side recording allows the stereo width to be adjusted after the recording has been made.

What Is Mid-Side Recording?

Mid-side recording is a stereo microphone technique that captures sound using two different signals. The mid microphone records sound directed towards the front of the recording setup, while the side microphone captures information from the left and right sides.

The side microphone usually uses a figure-eight pickup pattern, which responds to sound arriving from opposite directions with opposite polarity. These signals are then combined using a process called mid-side decoding to create a conventional left and right stereo recording.

The technique can produce a stereo image while preserving useful control over its width.

How Does Mid-Side Recording Work?

The mid signal provides the central part of the recording. The side signal contains information about the differences between sounds arriving from the left and right.

During decoding, the signals are combined to create the stereo channels. In a simplified representation, the left channel is created by adding the mid and side signals, while the right channel is created by subtracting the side signal from the mid signal.

This relationship is what makes mid-side recording particularly flexible. By adjusting the level of the side signal relative to the mid signal, an editor can change the apparent width of the stereo image.

Why Is Adjustable Stereo Width Useful?

Imagine recording the ambience of a busy street for a documentary. You want the recording to capture the surrounding environment, including traffic passing from different directions and people moving through the space.

A wide stereo recording might work well during an establishing shot, helping the audience experience the atmosphere of the location. Later, however, you might want to use the same recording underneath dialogue.

Reducing the stereo width could make the ambience feel less expansive and potentially easier to position within the overall soundtrack. With a correctly recorded and decoded mid-side signal, these adjustments can be made during editing rather than requiring a completely new recording.

What Happens When Mid-Side Audio Is Played in Mono?

One of the useful characteristics of a conventional mid-side arrangement is its relationship with mono playback. When the decoded left and right channels are combined equally into mono, the side information cancels, leaving the mid signal.

This means the central recording can remain available without the side information. However, this doesn’t guarantee that every mid-side recording will sound ideal in mono. Microphone placement, decoding, processing and the balance of the original signals still matter.

It’s always worth checking the final result through both stereo and mono playback.

What Equipment Do You Need?

A traditional mid-side recording setup uses a forward-facing microphone and a figure-eight microphone positioned as closely together as practical. Some dedicated stereo microphones and portable recorders also provide built-in mid-side recording options.

The signals need to be decoded correctly, either by the recording device or during post-production. Many audio editing applications support mid-side processing, although the exact workflow depends on the software.

It’s important to distinguish recording in mid-side format from applying mid-side EQ to an existing stereo file. The latter processes stereo information but doesn’t recreate microphone signals that were never recorded.

When Should Video Creators Use Mid-Side Recording?

Mid-side recording can be particularly useful for capturing natural ambience, environmental sound effects, live performances and other situations where stereo flexibility is valuable.

For example, a filmmaker recording a forest environment might want a wide stereo image for an establishing scene but a more restrained version underneath narration. A sound designer could also use the technique to create recordings that adapt to different parts of a project.

Mid-side recording isn’t automatically better than other stereo techniques, but it offers a useful combination of flexibility and control.

Building a More Immersive Soundtrack

Good stereo sound can add depth and atmosphere to a video, but width should always support the scene rather than becoming a distraction. Mid-side recording gives creators another way to control that balance, especially when working with environmental audio and sound design.

If you’re combining your own stereo recordings with additional music or sound effects, you can explore the RouteNote Licensing library for sounds that help bring the different elements of your production together.