How do you get thick and smooth background vocals?

Here is a question recently put to Audio Masterclass...

"How do you get background vocals to sound like Def Leppard?. That is thick and smooth as it is on Hysteria engineered by Nigel Green, mixed by Mike Shipley and produced by Mutt Lange. How did they do it and how would one go about it if you wanted the same today?"

One thing is for sure, Mutt Lange wouldn't want to reveal the tricks of his trade.

However, there isn't really a great deal of trickery involved. Only a little.

Firstly, it is clear from documentary videos that Mutt Lange performs many of the background vocals himself.

He doesn't appear to have an outstanding voice or vocal talent. But he sings very precisely in both tuning and timing.

So this is the first requirement - background vocalists who can sing precisely in tune and in time.

Let's suppose that you only have one person to perform all of the background vocals.

You could achieve a thick sound through multi-layered harmonies. But even if there is just a single background vocal line, it is possible to make it thick, rich and smooth.

If you record exactly the same line four times, then the result will be instantly thicker.

If your system has the ability to vary the speed at which it records, you could set the speed just a little slower on two takes - say 2% and 4%, and correspondingly faster on the other two takes.

Then when you play back the result at the correct speed, the harmonics of each recording will be shifted slightly differently. This is an 'instant thickener' and always works well.

Another method is to pitch-shift the tracks slightly. Pitch shift is measured in cents, where one cent is one-hundredth of a semitone.

If you apply shifts of -4, -8, +4 and +8 cents to the four tracks, then once again the result will be instant thickness. I prefer the previous technique, but this works fine.

Some delay plug-ins allow you to modulate the delay time. So the delay time varies cyclically. And because of this, so does the pitch.

If you process each track through a delay of say 100 milliseconds, with a different speed and amount of modulation on each track, then the result will have excellent thickness.

You can compensate for the delay by moving the tracks 100 milliseconds earlier in time.

Generally if you have more than one singer, then the result will be thicker already. But you can still apply all of the above techniques.

If you work out four background vocal lines, and you record each one four times according to the guidelines given above, you will have a 16-voice chorus that will be thick and smooth indeed.