4 Tips for Using Reverb on Acoustic Guitar
In a dense mix it can be tough to find space for acoustic guitar, while in a sparse track, the acoustic needs to fill up more real estate. Learn to use reverb in different ways to help place the acoustic guitar in the track.
By Charles Hoffman
Many genres involve acoustic guitar; Folk, Country, Indie Rock, Pop, and even some Hip-Hop songs. Adding acoustic guitar to your song, or building a song off an acoustic chord progression, is a great way to infuse your music with an organic feel. As you add more tracks into a song, the mix can start to feel cluttered and “busy.” Using reverb in various ways, you can help place your acoustic guitar in relation to other elements in your song, like the vocals.
I’ll be showing you how to use reverb to take advantage of the z-axis in your stereo field, fill out the mids and sides of your mix, balance panned elements, and evoke emotion. Not only will these techniques allow you to make space for acoustic guitar in your mix, but they can just as quickly be used to fill space when working with a sparse arrangement.
1. Create a Sense of Depth with Reverb
Listening to music through a stereo set of speakers allows you to perceive what is known as a stereo field. This stereo field is an illusory 3D space created between your speakers that will enable you to perceive your song as having width, height, and depth. Differences between the left and right channels of a stereo signal create width (x-axis), frequency plays a part in height (y-axis), and volume and reverb play a role in depth (z-axis).
By taking advantage of the full perceived length of each one of these axes, you’re able to add additional elements to your song without cluttering the mix. In some situations, the goal may be to find a way to make room for additional elements in a dense mix, while other times, the goal may be to fill out a sparse mix using creative effects.
Multiple factors come into play when modeling a room using reverb, but generally speaking, the longer the decay time and wetter the reverb signal, the further back along the z-axis the element is perceived.
For example, if you wanted to place a soft, arpeggiated nylon string guitar behind a dynamic folk vocal, you could reduce its level so that it’s quieter than the vocal and then send a significant amount of the guitar’s signal to an aux track containing a reverb with a long decay time.
The following audio example demonstrates a chord progression played three times. The first playback contains no processing, the second has Waves Renaissance Reverb applied on an aux track, and the third has heavy transient compression applied to the acoustic guitar. All the recordings have been level matched to ensure that you just hear the effect of the processing applied. There’s also a dry lead vocal that has been positioned front and center to provide some context for the acoustic guitar in the mix.
As you can hear, the reverb does a relatively good job of making it seem as though the guitar is further away, but with the addition of compression, this effect is enhanced. A compressor with a fast attack like the Waves CLA-76 Compressor / Limiter will work well for this application. To simplify things when you’re mixing, imagine your mix is split into a foreground, middle ground, and background. You’ll keep elements that you want present in the foreground, supporting instruments and vocals in the middle ground, and things like pads, sweeps and effects in the background.
The reason that compression helps push elements further back in your mix is that it emulates what happens in real life to sound waves that are produced far away from you. Imagine someone clapping their hands right next to your ear; it’s going to be extremely loud, harsh and potentially hurtful to your ears. If the person clapping their hands walks 100 yards away, the clapping will become quieter and the energy making up the transient part of the clap will have time to decay before it reaches your ears, applying peak compression to your mix mimics this effect.
The best way that I’ve found to go about creating clear layers along the z-axis is by using two different aux tracks, each with their own reverb. Label the first aux track “Short Reverb” and add a reverb with a short decay time. Now duplicate this reverb onto the second aux track, label it “Long Reverb,” and give the reverb a long decay time.
You can send a little bit of signal from each track in your song to the short reverb to create a cohesive sense of space while maintaining presence; this is usually all that’s required for elements in the foreground. Elements that are in the middle ground can benefit from the long reverb, while elements in the background can benefit from both the long reverb and heavy peak compression.
The reason I recommend duplicating the short reverb as opposed to using a different reverb for the “Long Reverb” aux track, is so that you don’t create a confusing perception of space. If the only difference between both reverbs is the decay time, there’s a better chance that your overall mix will sound more cohesive. Increasing the pre-delay time of the long reverb is an excellent way to create a bit of separation between the two reverbs while maintaining clarity.
If you choose to apply compression to push a signal even further back in the mix, you want to use a high ratio to really slam the peaks down. I’d recommend starting with a ratio of 4:1 and moving up to 6:1, 8:1 and 10:1 as necessary. In many situations, you want to preserve the punch of a signal while applying compression, but in this case, you want to do the complete opposite.
2. Fill Out Your Mix with Stereo and Mono Reverb
Now that you have a way to place acoustic guitar along the z-axis of your mix, let’s take a look at the x-axis (width). Recording acoustic guitar in mono is quite common, but so is recording acoustic guitar in stereo. If you’re working with a mono recording, you should have a couple of creative ways to add width to your song without feeling like you need to add more instruments.
Using a stereo reverb like Waves H-Reverb is one way to go about adding width; it requires very little work to implement, and can instantly convince the listener that your mono acoustic guitar is placed in the center of a broader soundscape.
The following audio example contains a mono acoustic guitar recording panned center and run through a stereo reverb. You should notice the diffused sound out to the sides, and the main body of the guitar in the center of the stereo image. This is a rather laid back and subtle way of adding stereo width to your acoustic guitar recordings. There are also dry backup vocals panned hard left and right to provide context for the guitar.
This technique is particularly useful if you’re trying to feature an acoustic guitar and draw a fair bit of attention to it; this could work during the intro or interlude of a track. Running the guitar through a fair bit of reverb will keep it feeling pushed back in the mix, allowing you to draw attention to dominant elements that have less reverb applied to them, like vocals during a verse or chorus. Your goal is to guide a listener throughout your song and direct their focus. Reverb assists with this.
The following audio example is similar to the last one, but the vocals are no longer dry; they’ve been treated like background vocals. This allows the mono guitar to shine through, even with the reverb applied.
Stereo acoustic guitar recordings can benefit just as much from mono reverb as mono acoustic guitar recordings can benefit from stereo reverb. When you layer reverb directly beneath the element it’s affecting, there’s the possibility that your mix will start to become muddy.
A great way to overcome mud is to send some signal from a stereo guitar recording to a mono reverb. If your reverb doesn’t have a mono option, you can use a utility device to perform this processing instead. By positioning the reverb in the center of your stereo image, you allow the clarity of the dry signal to shine through on the sides. This technique leaves a fair bit of space up the middle of your mix to position dry vocals, or a lead instrument. As demonstrated previously, layering dry sounds on top of reverberant sounds works just fine.
3. Balance Panned Tracks Using Reverb
Doubling a mono recording so that you can pan the original left and the duplicate right is a conventional technique for achieving stereo width. You just need to make sure that you introduce sufficient pitch and time modulation to the duplicate to ensure that the two signals are perceived separately from one another. A plugin like Waves UltraPitch will allow you to do this reasonably quickly.
An alternative to this technique involves balancing panned elements with a dedicated mono reverb. For example, if you’ve panned a hi-hat just left of center, you can create a mono reverb just for that hi-hat and pan it just right of center; this will help shift the weight of the mix from the left side, back to the center, without requiring you to perform pitch and time modulation. Similarly, you could pan a mono acoustic to the left side of the mix, send it to a mono reverb, and pan the reverb track to the right side.
4. Evoke Emotion Using Reverb
Reverb can do more than just create perceived space; it’s capable of evoking emotion. A reverb that sounds damp and dark can bring about feelings of sadness or misery, while a reverb that sounds bright and crisp can make you feel uplifted and happy.
You can hear how the reverb is filtered quite clearly at the end of the following two audio examples.
One of the easiest ways to shape the emotion evoked by reverb is by using filters. Following up your reverb with an EQ will allow you to cut away the lows and highs by varying amounts. A dark reverb may be low-cut at around 200 Hz and high-cut around 800 Hz. A brighter reverb may require a filter that cuts away more of the lows, such as between 300-500 Hz, and that allows frequencies of 3500+ Hz to pass through. Waves Abbey Road Chambers plugin includes a filter section that allows you to apply both a top cut and bass cut with two easily adjustable knobs.
My default mixing template has two reverbs on aux tracks, which are low-cut at 200 Hz, and high-cut at 2500 Hz. I find that this is a good starting point for most mixes, and I can tweak the EQ settings based on the direction of the track. When aiming to evoke emotion with reverb in your own songs, think about the vibe of the song and whether it will benefit more from a dark or bright sounding reverb.
Conclusion
Reverb is a fundamental mixing tool that can be used in many different creative and technical ways. When it comes to acoustic guitar, which often stands alone with a vocal, it’s vital that you have some different ways not just to make space for the guitar, but to fill space as well.
Want more on mixing with reverb? Get creative tips on electric guitar reverb processing.
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