How to Check Your Mix in Mono (and Fix What Disappears)

Your beat sounds wide and full in your headphones. Then you play it on a Bluetooth speaker and suddenly your hi-hats are gone, your vocal sounds hollow or the lead almost disappears. Chances are your mix doesn't hold up in mono. The good news: it's easy to check, and usually easy to fix. Here's why it matters, how to listen in mono in FL Studio and Logic Pro, and what to do when something vanishes.

Short answer

• Flip your whole mix to mono every now and then and listen whether everything is still there: kick, 808, vocal, lead and hi-hats.
• Something disappears or sounds hollow? Then some sounds are working against each other. Usually that's a stereo widener, a short delay used for width or a copy with its polarity flipped.
• Keep your low end, kick and lead vocal in the center and use width mostly for the stuff around them.
• Check your export with the free Master Checker. Among other things, it shows the stereo correlation of your file.

What does mono compatible mean?

A stereo mix has a left and a right channel. In mono, those two get added together into one signal. When left and right are similar, that works fine. When a sound is exactly opposite on the left and right, the two cancel each other out, partly or completely. That's phase cancellation.

A mix is mono compatible when it still sounds the way you intended after that summing: maybe a bit narrower, but with nothing dropping out or turning hollow.

Why check your mix in mono?

Not everyone listens on headphones. In its guide to mono vs stereo, iZotope lists places where music often plays in mono, like clubs, restaurants, stores and sporting events, plus mono Bluetooth speakers and smart speakers like Amazon Echo and Google Home.

Mono is also just a useful reality check. Without the width of stereo, you hear more honestly whether your balance works. A vocal that just sits on top of the beat in stereo can turn out to be too quiet in mono.

How to listen in mono in FL Studio

1. Open the Mixer and select the Master track.
2. Add Fruity Stereo Enhancer as the last plugin on the master.
3. Turn the Stereo Separation knob all the way to the right. According to Image-Line's manual, turning it right reduces stereo separation until left and right are summed to mono.
4. Listen to your hook and the busiest part of the song. Then toggle the plugin on and off to compare.

Image-Line also notes that the level can change, so make sure you're not just hearing a volume difference. Don't forget to bypass or remove the plugin before you export.

How to listen in mono in Logic Pro

1. Add the Gain plugin (under Utility) as the last plugin on your Stereo Out.
2. Click the Mono button. According to Apple, it outputs the summed mono signal on both the left and right channels.
3. Listen, and toggle the button on and off to compare.

Logic Pro also has a Correlation Meter among its metering plugins. Apple's Logic Pro documentation explains how to read it: +1 means left and right correlate 100%. If the meter sits to the right of center, your signal is mono compatible. If it moves to the left of center, there's out-of-phase material that can cancel out in mono.

Check your export with the Master Checker

You only see the meter in your DAW while the song is playing. Want to see your whole file at once? Drag your export into the free Master Checker. Next to LUFS and true peak, it shows the stereo correlation: how well your mix holds up in mono. If it lands below 0, your mix can sound thin or hollow on a small speaker. Everything runs in your browser and your audio isn't uploaded.

A value above 0 doesn't automatically mean everything is perfect. Use the number as a warning sign, then listen in mono yourself to find where it goes wrong.

What often disappears in mono, and how to fix it

Your vocal sounds hollow or far away

Often that's a widener or a short delay on the vocal to make it wider. iZotope points to exactly this: delay-based widening can make a vocal sound hollow in mono. Turn the effects off one by one and listen in mono until the problem goes away. Keep your lead vocal dry and centered, and give the width to your backing vocals, ad-libs or the reverb on a send.

Your backing vocals or doubles drop out

Did you copy a vocal and flip the polarity of the copy to get a wide effect? In mono, those two cancel each other out completely. iZotope says that trick only works in stereo. Record a real second take and pan it instead. Two different takes are never exactly the same, so they stay audible in mono.

Your 808 or bass gets weaker

Low frequencies are more prone to phase cancellation, iZotope writes, and don't benefit much from stereo. Keep stereo effects off your 808, sub and kick, and keep that low end in the center. Is your low end also clashing with your kick? Read how to mix 808 and kick so they don't clash.

Your lead or pad gets thin

A lot of synth presets come with stereo chorus, unison or a widener already turned on. Dial that width back a bit, or put the width on a separate layer and keep a mono version of the melody in the center.

Quick checklist for your next mix

1. Kick, 808, bass and lead vocal in the center.
2. Width mostly for backing vocals, ad-libs, percussion, pads and reverb.
3. After every widener or stereo delay, take a quick listen in mono.
4. No polarity-flipped copies to fake width.
5. Export your mix and check it in the Master Checker: stereo correlation, LUFS and true peak.
6. One last listen on a small speaker, like a Bluetooth speaker.

Mastering next? Read how much headroom to leave for mastering and how many LUFS you need for Spotify first.

Want someone else to listen?

After hearing your own mix a hundred times, it's hard to stay objective. Want a second pair of ears to finish your track? Check out mixing and mastering by NameOnTheBeat. Rather keep checking yourself and put your master next to a reference track? With Master Checker Pro you compare loudness, dynamics and tonal balance with a song that sounds the way you want to sound.

FAQ

Should my mix sound exactly the same in mono as in stereo?

No. It will always be narrower in mono, and that's normal. What matters is that nothing drops out and your balance still works.

Should I mix entirely in mono, then?

You don't have to. Some mixers start in mono to get the balance right, and iZotope recommends that too, but checking regularly works fine as well.

Is recording my vocal in mono a problem?

No. A lead vocal is almost always a mono signal, and that's exactly right. Mono compatibility is about what you do with it afterwards, like wideners and stereo effects.

What's a good stereo correlation?

Right of center (above 0) is mono compatible, with +1 being fully mono. If your mix goes below 0, there's out-of-phase material in it. Use your ears in mono to find out which part it is.

Looking for more free help with your mix and release, like an audio converter or a BPM and key finder? Check out all the free music tools.