How to Mic a Virtual Instrument

With a “virtual microphone,” of course . . .

By Craig Anderton

With traditional instruments, one of the usual rituals is placing the mic to capture the sound in the best possible way for your recording medium of choice. While most people think of this as “good mic technique,” what you’re really doing is making a judgment about what type of processing you want to apply to the signal. For example, a condenser mic will give a brighter sound than a dynamic mic; and moving the mic further away from the sound source to pick up more room ambience is like adding an ambience effect.

Another important element is the addition of room mics, because part of a studio’s sound is the sound of its room. A room with a suitable balance of reflective and absorptive surfaces, and good diffusion characteristics, can enhance the sound of whatever’s recorded in it because it wraps the sound with a sense of space. However, as many instruments are close-miked and these mics do not pick up much of the room sound, it’s common to set up mics within the room itself that record the signals reflecting off the walls, ceiling, and floor. The signals from these mics are mixed in at low levels so you get a “sense” of the room, rather than “hear” it.

When tracking a virtual instrument, it can be a constructive exercise to think how you would mic it if it was a “real” instrument, and process it accordingly. Many times, you’ll be rewarded with a more realistic, satisfying sound. For example . . .

STEREO PLACEMENT

With instruments like piano, part of mic placement involves creating a convincing stereo image. While this can be simulated for virtual instruments with reverb and delays, one of the simplest ways create stereo is by modulating panning with keyboard note position (Fig. 1): The lower the note, the more the image shifts to the left and the higher the note, the more the image shifts to the right.

Fig. 1: Keyboard notes are about to be assigned to modulate pan in Cakewalk’s Rapture, thus creating a stereo spread as you play from left to right. This option is available in many software and hardware synthesizers.

In some cases, this may be too “clean” of a spread — with a real miking situation, the left mic will pick up some sound from the right mic, and vice-versa. This tends to create a bit of a build-up in the center, as it “monoizes” the signal somewhat. To circumvent this, add a little ambience (see the next section) and pan it toward the center. This shifts the overall image a bit more toward the center, but without altering the position of the notes themselves.

Another way to add a slight artificial stereo spread is to boost the treble subtly in the right channel, and similarly boost the bass in the left channel. This can be effective for instruments like guitar and piano where the higher notes appear more toward the right of the stereo image (this assumes panning from the audience’s perspective).

ADDING VIRTUAL ROOM MICS

Don’t overlook the value of adding some ambience, even if it’s artificial. This isn’t about an effect like hall reverb, which is a whole other subject; what you want is a very tight ambience, mixed well in the background. Good options include a small room reverb set for minimum room size, or a multi-tap delay with the taps set in the 20-30 ms range (a little delay feedback might help too, especially if the feedback can be cross-channel — in other words, the feedback path bounces between channels). You can even create your own ambience effects with a few stereo delays (Fig. 2).

Fig. 2: The Drum Room Ambience FX Chain in Cakewalk SONAR provides four different reflections, each with a level control, along with some other options.

Furthermore, remember that room mics are invariably compressed. You can simulate this effect by adding a lot of compression to the ambience, and rolling off a bit at the frequency response extremes. The more you compress the ambience, though, the more important it becomes to mix it in the background.

CONDENSER OR DYNAMIC?

Condenser mics tend to sound brighter than dynamic mics, so when you “mic” your virtual instrument, think about what type of mic you would use in the real world. For example, loud sound sources are often recorded through a dynamic mic, which tend to accommodate higher sound pressure levels. So, if your virtual instrument has some added distortion, consider lowering the high frequency response just a tad to give that dynamic flavor. Trimming the high frequency response can also make it sound like you’ve moved the mic a bit further away from the sound source—a trick that can help an instrument “sit” better in the mix.

To tweak the response, consider using a shelving filter to very gently raise or lower the very highest frequencies to simulate a condenser or dynamic mic, respectively.

IS THIS SILLY OR . . . ?

Sure, we know we’re not dealing with real mics. But sometimes, thinking about how you’d mic an instrument can give you some clues about “accessorizing” your virtual instrument for the most seamless integration into your mix—and it can make a difference.

Craig Anderton is Editor Emeritus of Harmony Central. He has played on, mixed, or produced over 20 major label releases (as well as mastered over a hundred tracks for various musicians), and written over a thousand articles for magazines like Guitar Player, Keyboard, Sound on Sound (UK), and Sound + Recording (Germany). He has also lectured on technology and the arts in 38 states, 10 countries, and three languages.