[Editor’s Note: This article was written by Gary Gray and is the first of a two-part series. Gary’s production/engineering contributions to the TuneCore Blog have been incredibly helpful and we hope you enjoy the depths he goes into per topic! Check out Part 2 here.]

Throughout my 30 plus years mentoring producers and engineers, a few key questions from students stand out as repeating themes, and some of those questions tend to baffle not just the newbie, but even those that have spent a few hundred hours (or more) mixing and mastering. Here is one such question:

What IS the actual difference between mixing stereo tracks and mono tracks?

The deeper you look into this seemingly innocent question, the more and more it becomes clear that this question is really made up of multiple questions, and multiple layers of answers. In this article I am going to address all of those questions and supply the answers.

Ok, here we go…

Mono

The word Mono comes from the Greek word monos meaning “alone.”  In the sound recording and reproduction world, the word Mono is a shortened form of the words Monophonic Sound or Monaural Sound. Mono simply means a single audio signal, such as a voice recorded with one microphone, a guitar with one cable, a bass guitar with one cable, or a mono sample from a sample library — as opposed to two different audio signals (stereo).

“True Monophonic Sound,” or “True Mono” is reproduced with a single speaker.

However, many listening systems use two speakers. An interesting phenomenon occurs when playing a mono signal through two speakers. A term sometimes used to describe this phenomenon is “phantom mono.” 

How can two speakers create a single, centered, mono illusion? 

When you record a mono signal, the waveforms of the sound source will show up on a single plane in the middle of the track, exactly like this Mono Recording of a Lead Vocal Track:

Digital Audio Workstations (DAWs) are designed to take this single mono signal and branch it off into two equal signals; one going to the left speaker and one going to the right speaker. The result of two equal signals, each being sent to one of two speakers is the phantom mono phenomenon – the listener “hears” a phantom mono signal centered between the speakers, as if all the sound was coming from an imaginary third speaker situated exactly between the two actual speakers.

How does the concept of mono apply to mixing?

Any mono sound, compared to a sound with stereo elements is perceived by the listener to be tighter, more centered, less wide, with less space & less depth and more focused. This is why kick drums and many bass instruments and/or bass synths are often mixed in mono. 

Stereo elements, on the other hand, contain differences in the left and right signal, and thereby create an illusion of sounding wider, deeper and more spacious. “Ear Candy” is often “sweetened” with stereo mixing techniques.

Songs with vocals are mixed so that the priority focus is on the lead singer. Therefore, most producers and engineers opt for mixing the dry lead vocal signal in mono, while mixing the vocal effects, such as reverb and delays in stereo.

The “Tree” Formula of Mixing

You may have heard of the “Tree” Formula of mixing. The trunk of the tree, being narrow and singular, represents mono. It also represents the foundation of the mix. The trunk (mono) could include elements like the kick drum, bass and vocals and anything else you’d like to include in mono.

Remember, mixing is an ART which uses the tools of SCIENCE. You are not bound to any particular rules or formulas. The “Tree” Formula happens to be one approach you can choose to use or not.

Checking Your Mixes in Mono

Besides knowing that you have the option to use mono within a mix for elements such as the kick drum, bass, and lead vocals, there is another approach which utilizes the concept of mono applied to your overall mix that can help you raise your level of quality control.

If you get into the habit of checking your mixes in mono, you are often able to pinpoint potential problems in your mix that may otherwise be undetectable while mixing in stereo. Some of these potential problems include:

1. Elements mixed too wide, which will lead to certain parts of your mix going weak or even disappearing on certain playback systems. These playback systems include mobile devices (many mobile devices have only one speaker [true mono] and therefore playback in mono only), Instagram (Instagram converts your video audio stereo mix to mono on the iPhone App! Some people report success with a workaround App for IOS called Flume. [The Instagram Android App maintains a stereo playback]),  Also, if you’re a working DJ and create within any EDM genre, many clubs are set-up in mono. This is because a live audience is scattered all over a club and it was found that wide stereo mixes through stereo playback systems created “strange mixes” for people who were situated on the far left or far right side of a club.

Mono playback guarantees that everyone in the club hears the same mix. One trick that some DJ’s use to achieve great sounding live tracks in a club is to mix the bulk of their mix in mono and use the stereo field for any ear candy that they are willing to lose in a club. As I mentioned, overly wide mix elements can weaken or even disappear when played back through a mono system.

2. Another potential problem that can be spotted by checking your mix in mono is the problem of EQ weaknesses whereby several elements of your mix muddy-up, or are concentrated too much in certain frequencies. These can show up more clearly when played back in mono.

3. Another potential problem is your low end being out-of-phase (which creates weak, low volume, non-punchy low frequencies). This problem, if present, definitely shows up when checking in mono.

One way to completely avert the problems above is to mix THROUGH a mono mobile device in addition to checking your mixes in mono on your studio monitors. You can do this by using apps such as Airfoil, Satellite, SoundWire, TuneBlade, Stardock Acoustic Bridge, AudioRelay, SpeakerShare, AirMyPC, and Share Speaker Player. I do this rather than waiting until my mix is done – which used to create an overwhelming amount of wasted time in my workflow. Now, if a problem is there, I’m aware of it immediately WHILE mixing and correct it on the spot.

In fact, I’m able to make a very good living mixing and mastering industry standard recordings out of my home studio by setting up my workflow to include a switching system where I can check my mixing and mastering adjustments in real-time THROUGH a laptop, then THROUGH a mono mobile device, as well as through headphones and my studio monitors plus subwoofer – ALL THE WHILE A/B’ing WITH REFERENCE TRACKS THAT SOUND GOOD THROUGH MONO SYSTEMS.

Setting Up Your Studio To Check Mono

Some producers and engineers use True Mono in their studio set-up, whereby an actual single third speaker is situated between the two stereo monitors, and the output signal of the mix gets routed to that one speaker while checking mono.

This set-up has been used since the ‘70’s in major studios. You may have heard of the legendary Auratone Speaker Cube (jokingly referred to as Horror Tone Speakers by those who used them!) A newer company emerged to emulate the sound of Auratone Speaker Cubes called Avantone. Some producers and engineers use Avantone Speaker Cubes these days for true mono sound reproduction. Some prefer Auratone Speaker Cubes.  

Some producers and engineers route their output signals to one of their two monitors, muting the other speaker. Note: Both the right and left channel signals need to be routed to one speaker – you can’t just turn off one speaker and call that checking your mix in mono. There are specific ways to set this up. If you choose this set-up, do your research so you get the full benefits:

And some simply switch their DAW to mono and check their mix in mono through their two studio monitors:

Is there a difference in how your mix will sound if you route it to one true mono speaker, as opposed to a phantom mono playback with two speakers? Yes. It is slight, but it does exist. Routing the output of your DAW in true mono to one speaker will avoid a very slight phasing issue which occurs when using two speakers. True mono sounds just a bit cleaner and crisper and tighter than a phantom mono two-speaker set-up. However, this difference is very slight, and if you follow the revolutionary Mute Automation Checkerboard A/B’ing workflow I designed for use while mixing, it makes no difference which set-up you choose. Checkerboard A/B’ing is covered extensively in my online masterclass The Lucrative Home Studio as well as in this TuneCore article on A/B’ing.

You’ll notice that mono tracks have a single waveform, as opposed to stereo tracks, which have two waveforms, left and right – as you can see here:

A Common Myth Busted Wide Open

The illustration above shows a stereo image of a lead vocal track. In fact that stereo image above is an exported file of the mono lead vocal track you saw earlier in this article. Here, below, is that mono lead vocal track again. Compare the stereo track above to the mono track below:

The Myth

The Myth is this: “A Stereo File export or bounce of a mono track sounds different than the mono track. It sounds wider, more spacious, with more depth. In fact, any and every stereo track sounds wider, more spacious, with more depth, and louder.” 

The Truth

When you start with a mono track and export or bounce it to a stereo track, your DAW software will split the mono track into two equal parts, 50% of it into the left speaker and 50% into the right. The information on the left and the right are identical.

Both the mono track and its stereo export or bounce SOUND EXACTLY THE SAME through your speakers, mobile device, laptop or any device.

The Science

When a stereo file contains identical information on both the left and right side, the result is exactly the same as playing back a mono track. It IS a mono signal — it happens to be coming from a stereo file.

But I thought stereo means two! And stereo means wide!  And stereo means depth! And stereo means space!

As you can see, that is not always the case.

In addition, stereo has several definitions, which we’ll get into in Part 2!

Be sure to keep reading and check out Part 2 here.


Gary Gray is the teacher behind the Lucrative Home Studio online course. He’s an award winning composer, producer, and engineer, and has produced multiple projects for 20th Century Fox, Disney, Hollywood Records, A&E, EMI, CBS and many others in his home studio.

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