Fixing your audio mix: how to tweak that problem bass note

Here’s a quick and easy way to fix a fairly common problem with an audio mix after you have already mixed a song down to a single audio file.

So you’ve finally finished the audio mix for your latest song – no easy task if you tend to obsessively tweak your mixes way beyond the point where sane people would have stopped. I’m not saying I know anyone like that, mind you…

Anyway, your audio mix sounds pretty good in your home studio. But when you play the song on your iPod or in the car, you notice that the bass guitar notes are uneven – one or two particular notes always sound super loud whenever they occur in the song. This often happens even though you’ve applied compression on the bass track to try and prevent this very problem.

This is one of many audio problems that can occur when you mix music in a home recording studio, which is probably a converted bedroom in your house, and therefore probably not the ideal place for perfect audio. The boxy shape causes the sound to bounce around such that your room makes some frequencies sound louder than they are, and others sound not loud enough.

Anyway, so there you are in the car with your wife, listening to your song, and BOOM! – every time just that one note comes along, your skull shakes (and not in a good way) with how loud the bass sounds. Then everything goes back to sounding normal until the next time that note happens, etc. Your wife complains. And as usual, she’s absolutely right.

Why not just remix the song?

If you have the luxury of being able to just go back to your studio, open your mixing software (I use Reaper), and edit just the bass, then yes – that is what you should do. But what if someone else mixed your song for you? You probably don’t even have all the individual instrument files. All you have is the final song. What if you’re on the road away from your studio? Disaster? Nope. At least not with this particular problem. And the good news is this technique works just as well while you’re mixing as it does on the final mixed file.

Find out what note is popping out

The first thing you need to do is find out what note is rattling your bones every time it plays. I usually just listen to the recording and pause it just after the problem note plays. Then I hum the note to myself while holding my guitar, and play different guitar notes until I find it. You could do the same thing with a piano or any instrument you are familiar with. These days, you could even hum it into a tuner app on a smart phone.

So let’s just say the problem note is a B-flat, as was the case with “William Tell” (written by Ken and Lisa Theriot), from my latest album Outlaws and Bystanders. Take a listen to a snippet of the song and you’ll notice one bass note really sticking out, first at 2.66 seconds on the word “town,” then again at 9 seconds, again at 16.2 seconds on the words “bow to him,” and a couple of times in the chorus.

William Tell Problem

Find out what frequency matches that note

Every musical note corresponds to certain frequency. You’ve heard the term “A440?” That refers to the fact that the note “A” corresponds to 440 hertz (Hz), which means 440 cycles per second. However, it’s important to note that “A” doesn’t just occur once at 440 Hz. A standard piano keyboard has eight “A” notes on it. The note at 440 Hz is in the middle. The others are octaves, which brings up a fascinating point. An octave of any note can be found by doubling the frequency of that note (for a higher octave), or cutting it in half (for a lower octave). For example, if you double 440, what do you get? You get 880. So 880 Hz is an octave higher than A440. Conversely, cutting 440 in half yields 220. So 220 Hz is an octave lower.

How does this help? Well, we want to surgically reduce the volume of a very specific frequency in order to stop that one bass note from popping out. The tool for that is an equalizer (EQ), which won’t ask for notes – it’ll ask for frequencies. Once you know what note is causing all the trouble, you can consult a chart such as “Frequencies for equal-tempered scale, A4 = 440 Hz,” which a simple Google search turned up.

As I mentioned before, our song has the bass popping out every time it hits a B-flat. According to the chart, B-flat occurs at the frequencies of 29.14, 58.27, 116.54, 233.08, 466.16, 932.33, etc. Since it’s a bass note causing the trouble, we can pretty safely ignore the high frequency of 932.33 Hz. Since the meat of a bass guitar is usually found well below 300 Hz, let’s go ahead and try to turn down the volume at 233.08 with an EQ tool in Adobe Audition software.

I opened up the Parametric EQ tool in Audition, and as you can see, I typed “233” into frequency band number 3. Then as the song was playing, I turned down the volume by about 6 decibels (dB). But that had no audible effect. The note was still popping out. So I tried the next octave down, which is 116.54 Hz.

The Audition EQ tool gives you 5 bands to play with, so I just unchecked band 3 and tried 116.54 on band 2. Note that Audition rounded it up to 117, which is fine. Also, on both tests I used a fairly narrow bandwidth to make sure I didn’t accidentally pull down volume on other frequencies where other instruments might be affected. This time it worked like a charm! Here is the same audio clip as before, but with an EQ reduction of about 7 dB at 117 Hz.

William Tell Fixed

You may need to try a couple of different octave frequencies before you find the right one. But when you do, you’ll know right away. Of course you can use this same idea while mixing – just on the bass guitar track by itself.

I hope you find this helpful not only in your mixing, but also in editing audio after it’s already been mixed down. I know it saved my butt a few times.

EQ image via ShutterStock.com.

Ken Theriot is a singer, guitarist, and recording enthusiast who runs the Home Brew Audio blog, whose mission is to demystify audio recording for all the regular people out there who thought home recording was limited to the realm of tech geeks and audio engineers with lots of school and tons of expensive gear.

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