Tools for Mixing: Reverb
By Ernie Rideout
Of all the tools we talk about in the Tools for Mixing articles here at Record U, reverb is unique in that it's particularly well suited to make it easy for you to create clear mixes that give each part its own sonic space.
Reverb derives its uniqueness from the very direct and predictable effect it has on any listener. Since we humans have binaural hearing, we can distinguish differences in the time between our perception of a sound in one ear and our perception of the same sound in our other ear. It's not a big distance from ear to ear, but it's enough to give our brains all they need to know to immediately place the location of a sound in the environment around us.
Similarly, our brains differentiate between the direct sound coming from a source and the reflections of the same sound that reach our ears after having bounced off of the floor, ceiling, walls, or other objects in the environment. By evaluating the differences in these echoes, our brains create an image accounting for the distances between the sound source, any reflective surfaces, and our own ears.
The good news for you: It's super easy to make your mixes clearer and more appealing by using this physiological phenomenon to your advantage. And you don't even need to know physiology or physics! We'll show you how to use reverb to create mixes that bring out the parts you want to emphasize, while avoiding common pitfalls that can lead to muddiness.
All the mixing tools we discuss in this series — EQ, gain staging, panning, and dynamics — ultimately have the same goal, which is to help you to give each part in a song its own sonic space. Reverb is particularly effective for this task, because of the physiology we touched on earlier. As with the other tools, the use of reverb has limitations:
- It cannot fix poorly recorded material.
- It cannot fix mistakes in the performance.
- Any change you make to your music with reverb will affect changes you've made using the other tools.
As with all songwriting, recording, and mixing tools, you're free to use them in ways they weren't intended. In fact, feel free to use them in ways that no one has imagined before! But once you know how to use them properly, you can choose when to go off the rails and when to stay in the middle of the road, depending on what's best for your music.
Before we delve into the details of using reverb in a mix, let's back up a step and talk about what reverb is.
Reverb: Cause and Effect
At its most basic, a reverberation is an echo. Imagine a trombonist standing in a meadow, with a granite wall somewhere off in the distance. The trombonist plays a perfect note, and an echo follows:
Fig. 1. This is a visual representation of a basic type of reverb: a single echo. The listener hears a trombonist play a note, and then the subsequent echo. Even with eyes closed, the listener can picture how far away the reflecting wall might be, based on how long the sound took to reflect, which direction it seemed to come from, and its loudness.
Now lets put the trombonist on the rim of a large canyon. Once again, the trombonist plays a perfect note, and this time several echoes come back, as the sound reflects off of stone walls at differing distances and of differing angles.
Fig. 2. The trombonist plays the note again, this time from the rim of the Grand Canyon. The listener is also on the rim of the canyon, and hears the original note, followed by the subsequent echoes. With the diminished volume of each echo, the listener can easily picture how far away the canyon walls are. Even if each echo is a perfect copy of the original sound, as long as it diminishes and volume and seems to come from a location other than that of the original sound, the listener's mind places the trombonist in an imagined space.
Trombonists being highly sought after in Sweden, even to the point of being an imported commodity, let's put our trombonist in the Stockholm Konserthuset, one of the finest concert halls in Europe. This time, rather then producing a series of individual echoes, the note our trombonist plays generates numerous echoes that overlap in time, ultimately creating a wash of sound that decays gradually.
Fig. 3. Once onstage at the Konserthuset, the trombonist plays the note again. This time, the echoes are so numerous as to blend into a wash of sound. To the listener in the front row, still with eyes closed, the length of the predelay (the time from the initial note attack until the time the first reverberation occurs) and the length of the reverb tail (the gradual decay of the wash of echoes) provide enough information for them to imagine the size of the stage, the location of the walls, the height of the ceiling, and other characteristics.
Heading upcountry a bit, we'll put our trombonist in the Uppsala Cathedral, one of the largest medieval cathedrals in Scandinavia. Standing right in the middle of the cathedral, the trombonist blows a note and is immediately surrounded in a wash of reverberation that seems to last forever.
Fig. 4. In a cathedral, the note the trombonist plays seems to expand and reverberate endlessly as the sound reflects off of the many stone surfaces to cross and re-cross the vast space. The mind of the listener can picture not only the dimensions of the space, but also the material with which it's constructed, based on which overtones reverberate the longest.
Though simple, the reverb scenarios above represent aspects of how you can use reverb and delay to create sonic space around your tracks — and they explain why these effects are, well, effective. Plus, they also represent the real-world phenomena that inspired the creation of the reverb effects that are the basis of all studio reverbs. Let's check out some notable milestones in reverb development, as this knowledge will also make it easier for you to dial up the exact reverb effects you need.
Man-made Reverb: Chasing the Tail
For recording orchestral and chamber music, the simplest way to get a great reverb is to put the ensemble in a space that produces a great reverb, such as a concert hall or cathedral, and record the performance there. Of course, there are aspects of this that make it not so simple, such as the cost, the delays due to unwanted sounds caused by passing trucks or airplanes, and the lack of availability of such venues in general.
In the mid-20th Century, many recording studios were built with rooms big enough to hold large orchestras, in the hopes of re-creating that naturally occurring reverb. In some cases, these rooms definitely had a sweet sound. In many, however, though they could hold an orchestra, the sound was not reverberant enough.
There are many reasons that recording engineers are called engineers, and one of them is their resourcefulness. To overcome the reverberation situation, engineers would convert or build rooms in the same building as the studio, sometimes adjacent to it, and sometimes underneath it. These rooms would have a certain amount of reverberation caused by the surface material, the angles of the walls, and objects placed within the room to diffuse the sound. By placing a speaker in such a room and sending a recorded signal to the speaker, the signal would have the reverberation characteristics of the room. By placing a microphone in the room to return this reverb-processed sound to the mixing desk in the control room, the engineers could then add the processed signal to the original recording to give it the extra reverberative quality. This is the basis of the effects send and return capability found on almost all mixers, real and virtual. And when you see chamber or room listed as the type of reverb in a reverb processor, it's this kind of room they're trying to emulate.
Some studios succeeded in creating reverberation chambers that created a convincing reverb, such as those at Abbey Road in London and at Capitol Records in Los Angeles, which were used on the recordings of the Beatles and Frank Sinatra, respectively. But these didn't work for every kind of music, and you couldn't vary the amount of reverb time. There was definitely a market for some kind of device that would let engineers add reverb to a track without having to build an addition to their studio. Since steel conducts sound and transmits it well, plate reverbs were developed, in which a steel plate would be set to vibrate with sound introduced by a transducer at one end of the plate, and the processed sound would be captured by a pickup at the other end of the plate.
A German company called EMT produced the most popular of these in the late 1950s, which featured up to six seconds of reverb, a movable fiberglass panel that cold vary the decay time, a mono send input, and stereo return outputs. Their sound was smoother than that of a real room, but also darker. Though these were attractive attributes when compared to the cost and inflexibility of a reverb chamber, they were far from convenient: In their cases they were eight feet long, four feet high, and one foot thick! Consider that the next time you dial up a plate reverb preset on your processor.
What recording studios did have on hand were lots of tape recording machines. By sending a signal from the mixing desk to a dedicated tape recorder, recording the signal with the record head, and then returning the signal via the playback head to the mixing desk, a single echo of the signal was created, due to the distance between the record and playback heads on the tape recorder. This delayed signal could then be blended with the original. This is called a slapback echo, and it's prevalent on lots of rock and roll recordings from the 1950s. Even though the effect was just of one echo, it still imparted a sense of space to the instrument or voice to which it was applied, setting it apart from the other parts.
This poor man's reverb was improved when engineers figured out how they could take the tape-delayed signal from the playback head and route it back to the record head, creating multiple delays. This became known as tape delay, and crafty engineers developed ways to keep the sound from building up too much (feedback), so the effect would be of three or four quick echoes that got quieter with each iteration. This added another dimension to the spatial effect, and when engineers started sending this multiple-delayed signal into their dedicated reverb chambers, they discovered yet another useful reverb application.
Fortunately for you, there is Propellerhead Record, so you don't have to build underground rooms or rewire reel-to-reel tape recorders. In fact, you don't need anything except your computer and Record! No matter what hardware or software recording devices you work with, keep in mind the technology behind these historical developments, as well as our travelling trombonist, as we work with reverb applications in the next section.
It is Better to Send than to Insert
In each of the other Tools for Mixing articles, we created rough mixes using just the single tool featured in the article. We did this purely to explore the power of each of the tools brings to your music, not to suggest that you create a final mix using only panning, or EQ. In fact, in creating the rough mixes, we applied the tools sometimes to extreme levels, which you normally wouldn't do when crafting a mix. Normally, you'd use all your tools in equal amounts to make each track stand out just the way you want.
We're going take a similar approach with reverb, though in some cases, we'll actually grab the channel faders and make adjustments to achieve the full effect of placing sounds in the soundstage.
Another difference between reverb and the other mixing tools is the point at which it's best to apply it in the signal path: as an insert effect or as a send effect. Here's the difference between the two.
Fig. 5. Insert effect signal path: When you add an insert effect to a mixer channel, the entire signal for that track is processed by the effect, whether you've chosen a reverb, EQ, compressor, or any other effect. The only control you have over the amount of signal processing is with the effect's wet/dry mix, which is the mix between the unprocessed and processed signals. This method is best for effects that have more to do with the sound design of an individual track than with the sound of your overall mix. While you're mixing, it's a pain to go into the controls of individual insert effects to change the wet/dry mix. This limits your flexibility when mixing.
Fig. 6. Insert effect section in Record: Here is a mixer channel in Record that has an insert effect applied to it, in this case a very wacky vocal processor effect. It's easy to tweak the four available controls, two of which are active here, but it's not easy to adjust the wet/dry mix from the mixer.
Fig. 7. Send effect signal path: To process a track with a send effect, you engage the send effect, which splits the signal. The Send Level knob lets you set the amount of signal that gets sent to the effect. The processed signal goes through the Master Effects Return control, which lets you set the amount of processed signal you want to mix with the unprocessed signal via the effects return bus — a key element when it comes to mixing. Using the channel effects send controls in their default state, the send occurs post-fader (green arrow). In this mode, you set your send level with the Send Level knob. The channel fader then boosts or cuts the send level as you move the fader up or down, respectively, relative to the setting of the send knob. Any adjustments you make with the channel fader will affect both the track volume and the send level. The Return Level knob on the master channel determines the global level of the return signal mixed in to the master bus. In other words, the balance between the effect and dry signal remains proportional as you move the channel fader. If you choose pre-fader by clicking on the Pre button, then the channel fader has control over the effects send level as determined by the position of the Send Level knob (orange arrow). The level of the processed signal is determined only by the settings of the Send Level knob and the Master Return Level knob. Having these two options gives you a lot of control over how you blend processed and unprocessed sounds in your mix.
Fig. 8. Send effects in Record: This shows the overall effect send levels and effects in the Master Channel (1), the return levels in the Master Channel (2), an individual track send button and send level (3), and an individual track send button and send level with the pre-fader button engaged (4). In the examples that follow, we’ll be making most of our adjustments just with the individual channel controls.
Most engineers use reverb as a send effect, not as an insert effect. This allows much more flexibility and control during mixdown. You can easily achieve a more unified sound by sending multiple tracks to the same reverb, create individual locations for tracks by adjusting send levels, or distinguish different groups of tracks by applying different reverbs to all tracks in each group.
Since we're committed to giving you the best practices to adopt, we'll focus on using reverbs as send effects.
Create a Mix Using Reverb: Give a Single Track Its Own Space
This brief excerpt features a great Redrum pattern from the ReBirth 808 Mod Refill and a meandering Malström synth line triggered by an RPG-8 random arpeggiator pattern. The drum part is busy, to say the least. The arpeggio covers four octaves, and varies the gate length as the pattern progresses, resulting in staccato sections followed by legato sections. The basic levels are comparable. Give a listen.
The synth is certainly audible, but it gets lost in the ReDrum. Let's see if we can create some sonic space for it. We'll activate the default RV7000 plate reverb in the Master FX Send section by clicking on the first send button in the Malström channel strip.
Wow. That made a huge difference in the presence of the synth part. Even the low staccato notes stand out, and the smooth plate reverb seems to reinforce not only the individual pitches, but also the loping random melody overall. And that's just with the default settings, not even with any adjustment to send or return levels! Let's try the next default send effect by activating the second send on the Malström channel strip, which feeds a room reverb also on the RV7000.
The room reverb definitely gives the synth notes some space and makes them more present. But it doesn't have the smooth sustain of the plate reverb. Let's tweak the send level on the channel strip by cranking it up about 10 dB and see what that sounds like.
Increasing the send level had two interesting effects: It gave the synth its own sonic space, but that space sounded like it was way behind the drums! This is the basic idea of how you can use reverb to make one track sound like it's toward the back of the soundstage, and another sound like it's toward the front. More effect = farther away from the listener. We'll experiment more with this a little later. Now let's try out the next send effect, which is a tape echo created with a Combinator patch that uses two DDL-1 delay instruments and the tape emulation effects from a Scream 4 sound destruction unit.
The multiple echoes reinforce the sound while giving it a very distinct sense of space. This kind of effect isn't for all types of music, but it works great with a nice melodic synth patch like this. Let's try out the fourth and last default send effect, which is a very simple 3-tap delay from a single DDL-1 instrument.
Very interesting. There is no reverb per se applied to the Malström track, yet it sounds like it has reverb on it. It's more present in the mix as well. This is because on the sustained notes, even though we can't hear the echoes distinctly, they definitely create a sense of sustained reverb. On the staccato notes, you can still hear the delayed echoes, but since they're rapid and they decay quickly, they continue the apparent effect of reverberation. This is why engineers use both reverb and delay to help give each track its sonic space; even when used by itself, delay can create a very convincing sense of space.
This also explains why we had our trombone player go to the Grand Canyon earlier: To demonstrate that echo, delay, and reverb are effective variations of the same tool. What else have we picked up on?
- Increasing the send to a reverb makes a track recede from the listener
- Delay can have the same overall effect as reverb in a mix
Create a Mix Using Reverb: Make Tracks Come Forward and Others Recede
This track is a wacky bit of big jazz that has a brief feature for the saxophone section, which consists of soprano, alto, tenor, and baritone sax. Each part is angular and the harmonies are crunchy, to say the least. Let's have a listen.
You can hear that there are individual parts, but it's difficult to discern them, even though the tone is distinct for each instrument. They definitely don't blend, and there is not a clear sense of which instrument has the lead. Let's start by adding some room reverb to all four instruments, using the second send effect controls in each channel strip.
Putting the entire section in the same reverb space does help make them sound more distinct. It also makes the section sound like it was in the same room at the same time as the rhythm section, though they're obviously closer to the listener. It's a good start. Let's assume the soprano sax has the lead, and bring it to the fore a little bit more by increasing the send levels of the other three saxes.
Well those three saxes sure sound like they're in the background. But they're still just as loud as the lead soprano sax. Let's adjust their respective levels just a bit using the channel faders, to see if we can create the sense that the soprano sax is stepping forward.
By reducing the three lower saxes by 3 dB and boosting the soprano 1 dB, we've created a pretty convincing audio image of the lead player standing closer to the listener than the rest of the section. Musically, we've probably gone a bit overboard, as this might not be the best mix. But what the heck, let's switch things up and make the tenor player step out front.
Tenor players unite! With the tenor at 1 dB on the fader and -12 dB at the send, while its colleagues are all at -3 dB at the faders and 0 dB at the sends, we've created a clear picture of one instrument coming forward toward the listener and others moving away, even though it's not playing the highest part.
You can use these methods on background vocals, rhythm section tracks, and any tracks that you want to sound unified, yet at different distances away from the listener. The takeaway:
- Sending a group of tracks to the same reverb gives a unifying sound
- To bring a track forward, bring up the fader and reduce the effect send
- To send a track away from the listener, bring down the fader and increase the effect send
Create a (Rough) Mix Using Reverb
This blues track you may recall from other Tools for Mixing articles. We'll try the X-Games mix on it, using reverb and a little bit of level adjustment only to create a rough mix. As we said before, this is not a “best practice” for creating a rough mix. It is, however, a good way to learn what best practices are for using reverb and delay to create sonic space for each track in your mix. The track levels are consistent, and the panning is all right up the center. Let's give a listen.
We can hear all the parts, but the individual tracks are very dry. There's no sense of blend, and all the instruments are right up front. Let's start by putting the horns and drums in the back of the soundstage by increasing the channel strip send levels to the default room reverb and bringing down the channel faders a bit on the horns.
All right, now we've got a stage going on. The drums are still very present, but their sound is defined by the size of the stage. The horns sound like they're behind the guitar and organ, right where we want them for now. The guitar needs its own space, let's try some delay to see if that sets it apart.
Sending the guitar track to the tape echo certainly sets it apart. We also sent the organ to the room reverb, though not so much as to make it recede. It's starting to sound like a band. But there might be a couple more things we can do to make it sound better. One danger to sending groups of instruments to the same reverb is that the muddy low-mid frequencies can start to build up, and this might be the case with this rough mix. Let's see if we can't bring those down by editing the EQ on the RV7000 that's producing the room reverb.
Fig. 9. To edit the EQ on the RV7000, go to the Rack View, click on the EQ Enable button, and click on the triangle to the left of the Remote Programmer. This brings opens up the Programmer. Click on the Edit Mode button in the lower left corner until the EQ mode light is lit. The RV7000 gives you two bands of parametric EQ to work with, and for our needs, the Low EQ is all we need. Set the Low Frequency to its highest setting, which is 1 kHz, and crank the Low Gain all the way down. This creates a highpass filter that removes all the low and mid frequencies that were bouncing around our virtual stage due to the effect of the room reverb.
Ah, cutting the low EQ on the RV7000 helped a lot to open things up, but it still leaves us a sense of space. For fun, we also put some plate reverb on the guitar along with the tape echo, which really put it in a unique space that doesn't interfere with the other instruments. We sent the organ to the room reverb, to make it seem like it's part of the session, but still up front.
Perhaps not the mix we'd send to the mastering studio, but certainly one that shows how easy it is to use reverbs and delays to set up a virtual soundstage! The takeaway from this mix:
- Cut the mids and lows out of the reverb using the built-in EQ on the reverb itself; this will help keep your mix from getting muddy
- Send tracks to the back by increasing the send and bringing down the level
- Blend tracks where possible by sending to the same reverb
- Help individual tracks find their own space by sending them to a reverb or delay different from most other tracks
Combined with your mastery of the other mixing tools, your knowledge of how to use reverb and delay in a mix will help you get the mixes you want in a minimum amount of time!
Based in the San Francisco Bay Area, Ernie Rideout is Editor at Large for Keyboard magazine, and is writing Propellerhead Record Power! for Cengage Learning.
Part 7 - Tools for Mixing: ReverbPart 6 - Preparing a Space for Recording Part 5 - Recording Vocals Part 4 - Tools for Mixing: Levels & Panning Part 3 - Tools for Mixing: Dynamics Part 2b - Tools for Mixing: EQ Part 2a - Tools for Mixing: EQ Part 1 - Recording Guitar