Stereo, surround, atmos, binaural — all these formats and more are used to create an enhanced and compelling experience for the listener. They can trick the audience into feeling as though they were in the same room as their favourite musicians, or guide them on a sensory journey through their ears.

But as important it is to know and understand these formats, there is a powerful tool that every engineer should be aware of; one that remains as relevant today as it was 100 years ago. We are of course talking about monophonic sound, also known as (you guessed it) — mono.

A mono sound is any sound emanating from one position. The simplest way to get a mono sound is to use one microphone and one speaker. Sound will be recorded in a digital or analog track with only one audio channel and then played back from one speaker.

But what happens when we have more than one track or speaker? Simple: all the signals coming from different tracks get combined in one single channel and then sent to all the speakers equally. The same principle applies to turning any stereo track into mono. The two channels from a stereo track get merged into one and sent to the left and right speakers, or to one single speaker.

You can read more about stereo summing and its application for Middle and Side processing in our previous article.

Mixing in Mono

Mixing in mono can be a very powerful tool. It’s a technique used by countless engineers to get their mixes sounding clearer and better balanced. But it’s not only a technique, many phones or bluetooth speakers exclusively play sound in mono. That’s why making sure your mixes sound good in mono is still relevant today.

When we talk about mono compatibility, we refer to the ability to sum signals from a stereo recording or mix and preserve the balance of the audio with no masking or phasing issues occurring. Mixing in mono allows you to focus on the use of volume and EQ to create space in the mix, but it can also point out any potential issues that your stereo mix might have.

A common mistake when mixing in stereo (or any multi-channel format) is the use of the left and right channels as the main method of separating the elements in the mix. While stereo helps to bring a sense of space to the mix, it can cause masking between elements since they might occupy the same range in the frequency spectrum, and therefore making them unclear or muddy when played in mono.

Another common mistake is to duplicate the same track and then pan both left and right. While listening in stereo the mix might sound bigger, but in reality all we have done is doubled the volume of the track, which would ruin the balance that you think you had when it’s converted into mono. Delaying or inverting the phase of the duplicated track won’t do you any good either, since it will cause phasing issues or even the disappearance of that track altogether.

By leaving the pan pots centre while making the initial mix, we will focus on filtering, surgical EQ and volume automation. Then, positioning each element in the stereo field will enhance the listening experience and help to separate the elements further, whilst maintaining good mono compatibility.

Check Your Mixes

Having the option to flip your tracks to mono during the mixing process can be beneficial. Especially to see if any stereo effects or reverbs are still noticeable and not causing any issues.

Many studios will have a separate speaker to route the mix and test this, but you can do the same on your computer with a single plugin. Most DAWs come with a built-in plugin that allows you to turn your stereo mix into mono. An example of this is Logic Pro’s Gain plugin. Just place it as your last insert in your master track and turn on the Mono switch. Then, just bypass the plugin and keep it like that until you want to check the mix in mono. If your track still makes you bounce with the plugin active, you are on the right path. Just remember to bypass the plugin again when you want to continue working in stereo.

Do you check your mixes in mono? Do you struggle to find the right balance in your mixes when working in this format? Let us know in the comments and don’t forget to subscribe to our newsletter to learn more about mixing techniques.