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What is reverb in music?

Reverb is an often largely misunderstood part of how recorded music works.

Rather than being an added extra, the space in which a piece of music takes place, is as much part of the music as the guitars or drums.

Changing the reverb space can alter the final piece as much as changing any of the other sounds in the mix.

As I always do, let’s start by stepping right back to see the full picture.

Use your illusion

The first thing that we really must understand about reverb – all recorded music really – is that everything is illusion.

There is no Lionel Richie with an 8-piece band between my speakers singing about his ballerina girl dancing on the ceiling. There are a lot of pointers that allow me to feel like this is happening, but Lionel is not here.

Many who mix music never really understand this vital fundamental. It is easy to think that the recording is pristine and unchangeable as it is The Performance, and as such must be treated as though it has captured the soul of the musician.

We know this is not true about photos. The person in the photograph still has their soul. The photograph is merely a set of cues, or pointers, that helps us to construct our own vision of the person in our minds.

Don’t buy the delusion

When a sound is made, the person recording tends to think only of the sound itself. This often leads to recordings where the sound being recorded is rather buried in “room sound”.

The person making the recording is surprised that the recording seems nothing like what (to them) really happened.

Rather like this photo, “Poorly Hidden” by J. Rouse, the recording has a lot of grass, sky and no clarity on the bison at all.

Poorly Hidden - brain focus illustration

What this shows us is that the human brain focuses on what it wants to pay attention to, but recordings do not. It is the role of the recording and mix engineer to help the listener know what they are focusing on.

This leads people into the rather strange state of applying wall padding to their rooms, in the mistaken belief that you get good recordings by separating the sound from the room entirely.

This is like J. Rouse deciding that he will mow the grass and whitewash the sky so he can show us a bison. This does not lead to a satisfying result at all (let alone the story really being told here).

Just one guitar

In the panel on the left we have a room with a guitar doing nothing. Everything is very bland.

guitar sound in the room

Notice how the whole room lights up with reflected sound when a chord is played. We, the listener, may feel like we are hearing just the guitar, but we are, in fact, experiencing the sound of that guitar in that room. The room is as much part of the sound as the guitar.

Early rock recordings were made in a “live room”. The sound of the room was part of the recording. A great live room was highly valued. Look up The Stone Room, famous for Phil Collins’s “In the Air Tonight”.

As owning a studio became more expensive and more people were doing DIY recording, the live room was replaced with reverb units.

While we do tend to separate sound and room more these days, a good audio engineer knows that room is still relevant.

Setting the stage

A great recording always must have two parts:

  1. A story which is the actual action of the music and words.
  2. A scene in which the story takes place.

Think of a play in a theatre where a Raven quoth “Nevermore” at Juliette (or something like that); we have people doing things in a defined space. The space helps us to understand the context, and therefore what is happening.

While a play without a set is possible, it is not as easy on the audience. This is a large part of why films replaced plays. Also, why CGI is so heavily (over)used in films.

In music, reverb is used to create the scene or room in which the illusion of the song is constructed.

As an aside, one of the first uses of “artificial” reverb space in music was Holst’s “The Planets” in 1918, where the last movement, “Neptune, the Mystic” was performed with the choir in a room behind the orchestra.

At the end of the movement a door was gradually closed to create the sense of moving away, distance, and fading.

Artificial reverb

We will skip over chambers, springs, plates and other methods used and step right to electromechanical echo units, which were mostly tape based.

These devices suddenly opened up the possibility of setting the size of the space in ways that were not really possible before.

Lexicon 480L

Eventually these echo units were replaced with completely electronic versions that increased the control and possibilities.

This became an explosion with the appearance of digital reverbs that finally offered the ability to really create new soundstages.

The Lexicon (pictured) appeared in many top studios from 1978.

Ten years later, it was possible for anyone to afford units like the Alesis QuadraVerb, which contained enough power to create any space needed – along with EQ, chorus and delay.

From delay we shall grow

All artificial reverbs are created from delayed signal. This is done using a digital delay that “holds” a copy of the sound for a set amount of time before releasing it. This duplicates the bounce back echo one hears at the Grand Canyon.

With extra processing in the form of many delay lines, pitch, and tone, a very credible “room” sound can be generated. This can be seen and heard better in the accompanying video where I show how a reverb can be built.

Using reverb in a mix

This is the bit where people get excited, and sadly often make a bit of a mess. As usual, let’s start with the things that you don’t want to do:

  • Don’t overdo it – while it is easy to add lots of reverb, either lots of send or lots of reverb units, it is not the best way to do it. Matter of fact, too much of either is making swimmy-mud (not epicfulness).
  • Don’t assume it is good because it is easy – reverb plugins are easy to use, but hard to master. Not the knobs, but how space really works in the illusion we call recorded music.
  • Don’t use presets – presets are tempting, especially seeing they usually come with an evocative name like “Best Most Epic Vocal Verb Eva”. Don’t believe the hype and learn how reverb works so you can build the space that your song needs from scratch. Otherwise, it is like sending Celine Dion out with Cannibal Corpse as her backing band coz ur bro sez they is bangin’. It is a mismatch which ruins the songs.
  • Don’t impress your ego – like above, always remember that the scene that you are creating for your story needs to match, or while it may feel amazeballs to you, it probably makes no sense to listeners.

Now that we have a sense of what we want to avoid, let’s look at the technical set-up options. There are essentially two options for how reverb is used in a mix:

  1. Send – this is the default way of using reverb. Send allows the same reverb to be used by every part of the mix. This is not a result of technical failings of the past, but completely about how a stage play uses one stage set that all the actors prance about in. This is the “room” that the song happens in. Being able to send all the parts to this one reverb is 99.99999999% vital for making the song feel coherent. In this usage, the reverb signal is 100% Wet, as the dry signal comes to the Masters directly.
  2. Insert – is a secondary way of using reverb enhancing a single sound when the main send reverb is not enough. In this usage, the Wet/Dry balance must be set at the reverb unit. It is vital that this reverberated sound is sent to the main room/scene, or it will feel like that sound is elsewhere. That can seem arresting as you do it, but will feel broken to the listener.
reverb send and insert

What you never want to do is have one reverb on every channel, as that means that every sound seems to be in a different place.

All those rooms overlapping will feel cluttered. That cluttered feeling will probably then have you reaching for EQs and compressors to try to solve the wrong problem.

Sterry-erry-oh

Reverbs are usually a stereo output. This is because we have two ears and the sound bounding about the room becomes “disordered”, which adds depth to the sound. We often mistake that for width. Width is trivial, always work for depth.

Send reverbs are often mono – the reverb sums the left and right signals to mono before processing the reverberation goodness. This is not a failing (as some assume).

In that guitar room above, all the walls light up with orange guitariness. This means that reverb comes from “everywhere”. Summing the reverb input to mono – some, or all the way – makes sure that our room feels right.

Panning of the direct sound will place the sound in the width dimension, reverb will set the depth dimension.

True stereo reverb can have its purpose, mostly for insert uses, but take care that the stereo image isn’t “weird” as a result.

Remember that there is one room with the sound banging into all the walls, so both ears should receive roughly the same amount of reverb overall.

Changing that can seem like a win at the time, but a fail for the listener as the sound breaks the rules of nature.

Reverb types

I have deliberately left reverb types or shapes until a lot later. They are not as important as people think. Sure, they are relevant, but you can use any type, like Plate, to make any sort of space.

I know, boggles the brain. How the possibilities are used is what separates one mix engineer from another.

The main types of reverb shapes are:

  • Room – a relatively square room where reflections are even.
  • Hall – like a room only with a rectangular shape so there are long and short reflections.
  • Chamber – is rarer these days, but was literally a room made for reverb; usually with a speaker, microphones, and “furniture” that could be moved around to change the reflection behaviors.
  • Plate – was a metal plate that was made to vibrate with the music and delivered a very rich and even reflection.
  • Spring – was an earlier evolution of the plate concept and delivers a unique warbling feel commonly heard on early Country and Rock n’ Roll records.

People will list off what each of these shapes should be used on, but this is silly in many ways.

While plates can be great on vocals, this is not a rule. Romeo can be made to serenade Juliette from a UFO whilst she sits in Harry Potter’s cupboard (can’t be worse than the DiCaprio film :-O).

The reverb signal is often processed with pitch, tone, compression and saturation to deliver results that either minimize issues, like metallic ringing, or create a more pleasing result. These secondary processes are often what sets one reverb apart from another.

Many experienced mix engineers work hard on their reverb spaces so their send is in fact a “chain” and not just a single reverb unit.

When and how to reverb?

I notice that many people handle reverb in their mixes later in the process as if it is add a pinch of spice to taste – often by applying presets, flip, flip, flip, until they get bored or it doesn’t totally suck. This is not a strategy. It is at best an action.

Sun Tzu says in “Art of War” that one should always choose the reverb space for the music before playing it. Ok, he probably said “battleground” – dude was a bit war obsessed.

I strongly advise to build your reverb space first. This is akin to having the sets ready for the actors before they start the play. This helps everyone to know where they can and can’t walk, lest they bump into that weird kid pretending to be a tree.

Setting the space in which the song occurs helps you to make all decisions from a set reference. If the scene is outer space, you will mix elements differently from if the scene is the 3 meter3 dive that is the best Jazz & Blues hole in Memphis.

When lacking a stage set or scene, it is far easier to mix each sound alone + perfect, instead of for its role in the story.

I start every mix by deciding which sounds I am going build the mix around. These become the “spindle” of the mix, to which all later decisions are relative.

I will set up my reverb from scratch (not a preset) to deliver the space that I want the story to happen in using that spindle. I apply that to every sound in the mix. I use -12 dB of Send (or 0 dB Send with Return at -12 dB) as the default send value.

Drums, or the Rhythm Bus, may have less Send than synths or vocals, but it is vital that all sounds go to that reverb so every player is on the same stage in the same scene.

Speaking of Busses, if a sound is sent to a Bus, like drums & bass to the Rhythm Bus, I will turn off the reverb send for each of the individual channels and Send only from the Bus. The Bus will probably be processing those collected sounds in some way, like EQ & Compression.

The reverb needs to match that processed sound, or the results will de-laminate, i.e. reverb will not match what the listener hears and feel weird.

If adding an Insert reverb to build a synth sound, I will set the Send amount for the synth first. I then create the local reverb parameters within the main scene so that the synth never feels like it comes from a galaxy far, far away.

While the insert reverb may make for a distant sound, it is still within the main scene so long as it is well inside the main Send reverb.

Feed the reverb

Great mix engineers learn that things are never done with one action. A great result is always the result of a collection of processes working together. This does not mean loooooong chains of plugins but simply that a bit of this feeds that which sparks up the other.

While one reverb can be used to feed another – common with digital synths – it is often wiser to use delays to feed your reverb. This mimics reality, in that a room usually has a distinct bounce based on where the sound is in that room, particularly in the depth dimension.

Using a delay unit per channel (and/or bus) for echo helps to place the sound in space. This is not about getting technical clever with psychoacoustic math, but simply helping each sound to have a place front to back, which is called depth.

Because these echoes are part of the signal sent to the main “room” reverb, that reverb picks up and enhances those echoes too.

The same applies to other processes and effects. A little bit of well-placed EQ (and its attendant phase warping) will feed the room space.

Subtle phase, frequency and time shifts, like those from flangers, phasers, choruses, and very short delays that create resonances also help make sounds in the mix really shine.

Bonus

Here’s a great thing about reverb; it makes things sound beautiful – or good if beauty offends you.

While there has been some sort of trend to remove all reverb from mixes, this is commonly a truly bad plan as it leaves things sounding creepily present.

Like Ozzy Osbourne crawled into your bed whilst you were sleeping and is staring at you as you sleep. Eeek!

Reverb adds a layer of gloss onto everything when done right. This also has the bonus of helping to smooth imperfections like slight tuning issues.

Coupled with a modulating delay, reverb is a far nicer way of making your singer sparkle than using MeloTune (AutoTune or Melodyne).

Practice

There is no easy way to reverb. Like anything special, reverb requires practice, practice and then some more practice. While anyone can paste presets, it takes time to really feel space and learn to build and use it in a mix.

Reverb comes easily to some, just like playing the guitar or singing does to some. If it comes easily, that is the better path to take.

Be the guitarist or singer and bring in someone who is great with space as your mix engineer. Otherwise, while the pasted reverb may be ok, it is not selling you to your potential audience.

Would you go to a job interview with mismatched and dirty clothes? Probably not. You’d get yer Ma to iron ya Sundee Best.

Bring in a mix engineer who is a natural with reverb space so your songs sound their best.

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