Noise Gate Ducker

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Credits

I've recently been working on a track with a friend that included vocals, guitar, bass guitar and percussion.

After listening back to the recording, it became clear that the guitar was competing with the vocal.  The guitar felt like it needed to sit back a little in the mix and ‘duck’ slightly while the vocal was present.

I recalled a technique I had read about in ‘Mixing Secrets for the Small Studio’ which uses a gate to achieve this.  The book’s author, Mike Senior, is also a regular contributor at Sound on Sound.  If you don't already own this book, I would seriously recommend it.

The technique involves using a noise gate to achieve a ducking effect.  I've owned the book for a while now, maybe 3 years or more and it was a great opportunity to put into practice more of what Mike covers in the book (page 221-222).

So, to solidify the technique in my mind I decided I would document it in this article.  Hopefully someone else out there will be able to take something from this article if they find themselves in a similar situation. 



Method

Here are the steps so that the guitar ducks out of the way of the vocal:

1. Create a new set in Ableton Live.

2. Create an audio track called ‘Guitar’ and lay down some guitar chops.

3. Create an audio track called ‘Vocal’ and lay down some vocals.

4. Create a return track, let's call it 'Noise Gate Ducker'.

5. Send 100% of the guitar track to the noise gate ducker return track you created in step 4.

Fig 1. Sends from guitar

Fig 1. Sends from guitar

6. Add a gate to the noise gate ducker return track and group it to create an audio rack.

7. Expand the gate toggle, enable sidechain and select the vocal track.  Set the gate's threshold to below that of the vocal level so that the gate will open when triggered by the vocal.

8. Add add a utility after the gate and enable its left and right phase.  This will reverse/invert the polarity of the guitar signal when the gate opens resulting in phase cancellation.  As the main guitar track and return track signals are identical and 100% (or 180 degrees) out of phase, they will completely cancel eachother out.

Reversing the polarity will take all positive amplitude values from the guitar signal and make them negative.  It does this by multiplying the values of the signal by -1.

This will cause the main guitar track to be silenced when vocal triggers the gate to open.

When the vocal signal is below the threshold (i.e. there is no vocal), the gate will close, phase cancellation will cease and the guitar track will return to the mix.

Fig 2. Noise Gate Ducker

Fig 2. Noise Gate Ducker

Note the following gate settings:

Lookahead - set this to zero so that there is no latency delay on the gate, you'll get some nasty feedback if not, at least that is what I found.

Floor - set this to -infdB so that the guitar signal is muted completely when the gate is open.

Release - set a generous release so that the guitar returns to the mix gradually.

Attack - set this quite low as it will determine how quickly the ducker is applied.

Frequency - set this to cause the gate to be triggered by a specific band of frequencies rather than just the signal itself.

9. Set the fader level on the return track to control how extreme the ducking is.  0dB phase canellation will produce more extreme results, so lower the fader level to achieve a more subtle duck of the guitar track.  In the Ableton Live pack, I have used a more extreme setting to emphasise the ducking.

Fig 3. Return Fader

Fig 3. Return Fader

10. Play the guitar and vocal tracks. 

What you should hear when the vocal ends, the main guitar track comes back up in the mix.

What you’ll see in the noise gate ducker is illustrated below.  The vocal drops below the threshold and a red bar fills up the gain reduction from top to bottom.  This is because we have floor set at -inf dB.  As this happens, note that the return track’s level (in green on the right) drops off a cliff.

Fig 4. Noise Gate Ducker In Action

Fig 4. Noise Gate Ducker In Action

11. Now export the master track to an mp3 or wav file and the guitar duck is clearly audible:


What Next

I'd recommend you have a go at the steps above.  If like me, you're the type of person who learns by doing, it will help understand what is going on here if you get stuck in and build it from scratch.

Alternatively, if you're short on time there's an Ableton Live Pack which contains the noise gate ducker at the bottom of this post you can download.

Either way, when you have set up up your noise gate ducker, save it to your user library so you can drop it in when required.

If there are other tracks you would like to duck, you can send these to the noise gate ducker too and control the level of ducking for each track through each tracks send amount

If you enjoyed this post, I’d be very grateful if you’d help it spread by emailing it to a friend, or sharing it on Twitter or Facebook. Thank you!