By Jon Chappell
Guitarists have something of an “interesting” relationship when it comes to stereo. As listeners, we like our stereo sound, just like everyone else with two ears. But when it comes to recording, the meaning of stereo requires clarification. Not many guitarists play live in stereo, even if they do employ two speakers for dispersion or increased volume.
In recording, stereo means two tracks and separate signals for the left and right outputs. True stereo means these tracks were recorded as two separate sources—such as two mics in an X/Y pattern. Simulated stereo can be achieved by taking a mono source (say, one mic or one cord from the mono out of your multi-effects), adding stereo effects, and splitting the signal in the mixer so that effects come out in stereo, but the guitar sound itself is the same on both left and right channels.
In a normal stereo configuration, two inputs come into the mixer, each carrying a separate signal, even if these individual signals contain elements of the other sound, which they would if they were microphones in the same room. You can send these channels directly to the stereo output, preserving their Left/Right orientation by keeping the pan knobs rotated hard left (fully counter-clockwise) and hard right (fully clockwise). This way, the signals’ independence is preserved (i.e., they don’t mix), as shown in Fig. 1.
Fig. 1. In true stereo, signals are separate, even if the mics pick up sound from the other source (which is natural). On a mixer, the signals are kept separate by being panned hard left and right when going to the stereo bus (output).
If you’re a guitarist, most often you’ll track (that is, record to disc or tape) your axe as a single source, in mono, using one track (designated, numbered location on the DAW). This usually means you’ll have one mic in front of your instrument (if acoustic) or amp (if electric), or you’ll provide one line output from your amp, multi-effects, interface, or plugged-in acoustic to feed the board. If this is the case, your signal is going to a single channel of sound recorded to a single track. One track is always mono. It can become simulated stereo later on down the line, but you’re really recording in mono here.
And just because you use two tracks for one guitar doesn’t always mean you’re recording in stereo, either. For example, a common case of two mics in a non-stereo configuration is combining a close-miked amp and distant-miked amp (which picks up more of the room, or ambient sound). This is known as layering or blending. Here, each mic goes through its own channel, just as it would in a stereo setup. But the difference is, we don’t want these two sounds to be heard as coming from two different places in the stereo field. So we combine the sources into a single sound by routing them to a bus (an extra channel that accepts multiple channels). The bus then feeds the stereo output with two identical sounds (the blend of the two mics), as shown in Fig. 2.
Fig. 2. In a layered sound, the different guitar sounds arrive on separate channels or tracks (just as in a stereo signal). But then the sounds are combined when they’re routed to a bus, which in turn feeds the stereo output. The level is raised or lowered by moving the bus fader; the quality of the blend (close mic vs. room mic) is altered by changing the positions of the individual channel faders.
When you mix the guitar sound with the rest of the band, you use the bus’s volume fader to raise and lower the volume of your carefully crafted blend. To vary the actual balance of close-mic and room-mic sound, you move the channel faders. But once it’s routed to a bus, that composite signal is treated as a single source when it’s sent to the L/R output.
The phrase “placing it in the mix” can mean several different things, depending on the context. It could mean where in the stereo field a particular sound sits. It could also refer to the front-to-back placement, which depends on two factors: 1) the relative loudness of one sound to the others; 2) and the ambient effect level (reverb) relative to the dry sound. Since we’re talking about stereo, let’s deal with the more basic of the two strategies—position in the left-to-right sound field.
To place your single track of guitar anywhere in the stereo field of a mix, you need only to have the sound assigned to one mixer channel or bus, provided that channel or bus has a pan knob. All the pan knob does is change the volume levels in the two channels in the stereo (L/R) bus, which you hear through headphones and speakers. Pan works on both channels simultaneously, in a ratio. For example, at a 50/50 ratio, the sound is equal in both channels and sounds like it’s coming from the center (sometimes called a phantom image, because the speakers are usually well to the side of the center position).
Hard left, hard right, and center are pretty easy concepts to grasp. Where you have to put your thinking cap on is figuring out how those in-between locations are achieved. Obviously, you can’t physically have a sound emanating from in between hard left and center (because there’s no actual speaker there), but you can create the effect psycho-acoustically. By having the majority of sound come out of the left speaker with just a little bit of sound from the right, you can create the effect of the location that is neither hard left nor center.
You can cause your sound to move continuously from hard left (sound coming from the left speaker only) to hard right (right speaker only) by slowly sweeping the pan knob from left to right. Although it sounds like your guitar is going gradually across a virtual sound field in front of you, all you’re really doing is changing the relative volume of the left and right channels, which gives the illusion of the sound traveling from left to center to right, and various points in between. Keep in mind, this is not stereo sound or stereo recording, but placement of a mono sound in the stereo field.
Look at Fig. 3, which shows a seven step stereo field. (You can have any infinite odd number positions to represent the stereo field, but seven is a good working number.) Underneath the seven positions in the semi-circular sound field are the corresponding speaker loudness diagrams with the appropriate loudness levels indicated in red. Notice that as you scan the speaker diagrams, you see the right level go down as the left level rises, and vice versa, in a reciprocal action, like a seesaw. But the effect to the ear is that the sound is moving continuously from left to right—even through locations where there is no speaker.
Fig. 3. As the relative loudness changes between the two speakers from #1 to #7, the listener will perceive the sound moving continuously in the stereo field from left to right.
So what’s all this pan stuff got to do with music? It’s quite simple: in order to create a proper illusion of musicians playing, you have to put them in relative horizontal positions in front of the listener. If you have multiple instruments playing different parts, it’s a good idea to delineate them with respect to placement in the stereo field.
In a real-world example, let’s say you have three guitars: one guitar playing full chords; another playing low notes and riffs; and a third playing up-the-neck, high-string chord inversions. One approach would be to put the chording guitar straight up the middle (panned center), the low-note guitar slightly left, and the high-note guitar slightly right. This allows the listener to hear each part in its own space a little better than if all three guitars were panned center. Fig. 4 shows how the listener would experience this cycle acoustically.
Fig. 4. The low-note guitar (green) and high-note guitar (red) will each appear slightly to one side, while the chording guitar (yellow) appears to come directly from the center of the stereo image. This allows the guitars to mix their sounds together slightly while maintaining a separate location, or identity.
Each instrument will be present in both channels, but because of the different pan positions—really, varying levels between the two channels—the listener will perceive the guitars as in separate “locations,” which helps in hearing the individual parts a little more distinctly. If you didn’t want this, you’d simply pan all three center, and you would have a straightforward layer. But to best showcase three disparate musical roles, it’s better to employ a little judicious panning.
There are lots of discussions and disagreements about what stereo is. But as long as you know how to be specific about which version of “stereo” you’re using when recording, you can use the concepts of sound-field placement and blending to their best effect. It's important to separate this from the more complex operation of true stereo recording, where two discrete signals are preserved from the beginning to the end of the recording process.
Jon Chappell is a guitarist and Associate Editor at Harmony Central. He has contributed numerous musical pieces to film and TV, including Northern Exposure, Walker, Texas Ranger, All My Children, and the feature film Bleeding Hearts, directed by actor-dancer Gregory Hines. He is the author of The Recording Guitarist: A Guide for Home and Studio (Hal Leonard), Essential Scales & Modes (Backbeat Books), and Build Your Own PC Recording Studio (McGraw-Hill), and has written six books in the popular For Dummies series (Wiley Publishing).