Every great audio production begins with a great recording. Achieving a quality recording depends on several factors: performance, instrument fidelity, acoustic room treatment, and, of course, the microphone(s) you use. Indeed, the mics you employ for a particular recording and how you arrange them can make or break your production from its earliest stages. Knowing a thing or two about various mic configurations gives you a significant advantage in the studio, as well as additional freedom to experiment. Mid/Side recording (or “M/S” for short) is one of many stereo recording techniques with a wide range of applications. Let’s get to the heart of M/S recording and see why it’s worth incorporating in your productions.

What Mid/Side Recording is and Why it Matters

M/S recording is a stereo recording technique that gives the mixing engineer complete control over the recorded audio’s stereo field (i.e., how far it’s panned left and right). Better yet, this flexibility is afforded to you after the recording has taken place. In other words, setting up your microphones in this manner gives you the freedom to adjust a track’s stereo spread at your leisure. Moreover, M/S recordings are easy to collapse into a centered mono track for more precise mixing, and they’re highly phase coherent.

A Primer on Stereo Recording

Stereo recordings are common in modern music production. To record in stereo means to record a single source with two mics (one for the left channel and the other for the right). Stereo recordings provide a sense of space, giving the listener a more dynamic experience that spans each ear and the spaces in between. Of course, recording in stereo isn’t without its challenges. As we discussed in our previous blog, “Audio Phase: How It Works And Why It Matters,” recording one instrument into two channels can introduce phase problems. Depending on the distance and angle between two microphones, the resulting audio can take on a different quality when listened to in stereo vs. mono (i.e., a single channel).

Audio engineers and producers have developed specific stereo recording techniques over the years to anticipate potential phase problems. Mid/Side (MS) recording is one of these tried and true methods, but it’s not the most popular one – the “X-Y” technique has earned that title. This setup has the two mics facing each other in close proximity (usually one just above the other), forming a 90-degree angle. Other methods such as “ORTF,” “Spaced pair/A-B,” and “Decca Tree” are also commonly used stereo miking configurations. Each of these stereo recording techniques is worth exploring in its own right, but we’ll focus on the M/S method for now.

Making Sense of Mid/Side (M/S) Recording

The name of this technique neatly reveals a bit about its setup. Essentially, one mic is placed in a central position (ergo, “mid”) while the second is turned to its “side” 90 degrees and placed directly above or below the first. One mic captures the audio coming straight at it in this position while the other captures the stereo spread. Not just any two mics will do for this configuration to pan out (no pun intended). As a general rule, you’ll want to invest in two different kinds of mics for this setup to work. You can also get away with using two similar mics, but only if each one is configured with specific pickup patterns. The “Mid” mic should receive audio in a cardioid or hyper-cardioid pattern to pick up sound primarily from the front; the “Side” mic needs to pick up audio in a figure-8 pattern, which is to say from the left and the right. As a result, one channel will mainly receive the sound head-on while the other will pick up the room’s reflections from the left and right sides – each mic’s active zone is the other’s dead zone or “null spot,” resulting in a centered, coherent image.

This video from RecordingMag does a great job explaining and showing how the M/S setup works.

The Many Benefits of M/S Recordings

You might wonder why some people decide to use this stereo recording method as opposed to others. While all stereo recording configurations deliver specific benefits, the M/S technique is a solid all-around choice. The three main advantages of setting up an M/S recording are flexibility, control, and mono compatibility.

First, let’s flesh out the flexible aspect of M/S recordings. As mentioned earlier, you can use different mics to achieve a worthy M/S recording – this isn’t always the case for other stereo recording techniques. With X-Y, ORTF, and spaced pair recordings, for instance, both mics usually need to be identical. For M/S recordings, you can experiment with various mics for each channel, so long as they’re configured with the polar patterns mentioned above. M/S recordings are also flexible in that they offer the engineer/producer far more influence over the stereo image than other setups, which brings us to the following benefit: control.

When recording with the M/S method, stereo imaging is entirely based on the amount of signal received by the left and right sides of your figure-8 microphone. Adjusting the volume of either the mid or side mic will expand or contract the stereo sound accordingly. This means that you can freely control the width of your M/S stereo recording after the fact. For instance, if you were to bring the mid-channel all the way down, it’ll leave you with an ambient, panned room sound. Conversely, if you lower the side channels to zero, you’re left with centered, mono audio. Most other stereo recording setups don’t offer this level of mixing manipulation.

That third benefit of M/S recording – mono compatibility – is more valuable than you might at first realize. As discussed in our blog post on audio phase, mixing in mono is a clever and convenient way to identify phase issues and clarify your mix. If you only mix in stereo, you can easily miss why your production sounds muddy in certain areas – mixing in mono can help pinpoint the problem. And when you record in the M/S configuration, you’ll have easy, pure access to the mono track.

Setting Up an M/S Recording

Now that we’ve established what M/S recording is and why it’s so useful, you might be eager to try it out for yourself. Without further ado, let’s outline how to set up an M/S recording step by step.

For starters, you’ll need to pick out two microphones (as mentioned earlier) as well as two reliable stands, cables, preamps, and input channels (“stereo” basically means two of everything). From there, set up your mid microphone as if you were preparing to record in mono, at the proper distance from the audio source. Then, place the side microphone directly above or below it, making sure that it’s positioned precisely 90 degrees to the central mic (i.e., facing left and right). Configure each mic with the proper polar pattern (cardioid for the mid mic and figure-8 for the side). Once you’ve got your mics in the proper position, it’s time to set up the digital side of things (this is where stuff gets a bit more technical).

As with any other stereo recording setup, each mic’s signal is sent to its own track. For M/S recordings, though, each channel must be matrixed and decoded to deliver a true stereo image in your digital audio workstation (DAW). Consider that your side mic is capturing both the left and right sides of the audio at once. In other words, one mic is essentially doing the legwork of two; because of this, the side signal must be broken up into two channels (you can do this in your DAW or physical mixer). Either way, you need to pull up the side signal on two distinct channels then reverse one of the signal’s phases. Then, you must pan one side completely to the left and the other all the way to the right. Now, your side microphone will deliver a unique left and right channel. Ultimately, the M/S recording configuration results in three channels: central, left, and right – even though you’re only using two mics.

Stereo Recording: Taking Sides

That’s M/S recording in a nutshell. The more you experiment with this and other stereo recording techniques, you’ll find unique applications and configurations that work for your productions. There are many uses for M/S recordings, and the benefits mentioned earlier speak for themselves. Having a more significant amount of control over the stereo field is a powerful tool in the art of both mixing and mastering. Indeed, M/S configurations can make your tracks sound broader and more dynamic – eMastered can take that expansive sound even further with our automated mastering services.