How do you Mic a Virtual Instrument?

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 (Figure 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.
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 a bit. 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 bit of an artificial stereo spread is to boost the treble slightly in the right channel, and boost the bass slightly 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). This has to be done subtly, of course.

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).
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 would be used in the real world. If you’re synthesizing a “guitar-like” sound, consider adding a bit of brightness to the sound to simulate more of a “condenser” effect. Similarly, loud sound sources are often recorded through a dynamic mic, which as a group 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.

JARGON JOCKEY

Room mic:
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, these mics do not pick up much of the room sound. As a result, it’s common to set up mics within the room itself that record the signals reflecting off the walls, ceiling, and floor. As these signals are weak (and often compressed), you want to use a mic with as low a noise floor as possible, and mix the output low enough so that you get a “sense” of the room, rather than “hear” it.