Microphones: Resonance, Rhythm and Reverberation

Somewhere, you'll find a place that captures the sound of the musical note the best. Start by putting your mic there. You might still move it around a little afterwards, but it's a good place to begin.

Moving the microphones is one of the most creative, challenging, and deeply satisfying parts of professional sound. Whether in the studio or on the stage, slight changes in the positioning can make a big difference.

The first place most of us start with an acoustic guitar, or any stringed instrument, is to place a mic near the sound port.

In a recording environment, we leave room to play around and create sound. In live sound, though, concerns like feedback, stage visuals, sound bleed from other instruments and even change over time between bands, can box us in to a quick and safe routine.

No matter the circumstances, though, the fundamentals of mic placement still ring true and should not be overlooked. We all form habits in live sound. It's a necessity. Take the time to occasionally ask if there is an option to consider that's beyond simply "the way we always do it."

One instrument I find myself in a rut right now is with the acoustic guitar. Lately, practical concerns have made my acoustic setup an effective, but boring "out to DI box." Over the years, though, I've learned many fun ways to capture acoustic guitars, violins, mandolins and a variety of other acoustic strings.

I broke into the live sound side of the industry in coffee shop venues, where delivering a rich sound the artist loves is critical. Some people like their violin to sound smooth and graceful. Some like their guitars to pound along like a locomotive. Others are trying to capture an accurate and uncolored vibe of their instrument in the hall.

Talk to your performers and agree on a place to start, then get in there and move the mics!

Resonance

The first place most of us start with an acoustic guitar, or any stringed instrument, is to place a mic near the sound port. The port in a stringed instrument is where the musical note resonates the loudest.

As the strings cause the wood to vibrate, the air inside is excited and pushed out of the port. It's the same underlying principle as blowing across a bottle top, known in acoustic physics as the Helmholtz resonator effect.

Different instruments have different types of ports. Violins, mandolins, and certain guitars and bass have "f" ports. Banjos may have resonator plates in the back to help direct the sound forward through the body.

What about something unusual, like a harp? I don't mic harps often myself, so a sort of strategy needs to be applied to figure out how to catch the resonance. The best guide is to go onto the stage and listen. Move around the instrument, placing your ear near the strings, near the soundboard, near the column.

Another option is to listen next to the performer's ears, as it can be cool to hear what they are hearing (depending on the performer and instrument).

Somewhere, you'll find a place that captures the sound of the musical note the best. Start by putting your mic there.

You might still move it around a little afterwards, but it's a good place to begin. This same technique works great for more common instruments as well.

Rhythm

In addition to the pure tone of the instrument, acoustic strings have a phenomenal rhythmic quality.

For an aggressive guitar player, adding a mic across the soundboard aimed at the strings can produce a really hard, striking sound as the pick slams against the nylon, gut, or metal. This can cut through a mix, sometimes even better than the more musical and round resonance.

There are so many ways to approach it.

Instead of just placing a mic in front of the hole on an acoustic, try placing it in front of the 12th fret, close to the musician's hand. Placed a distance from the port, this imparts the much brassier and hard-hitting sound of the strings on the soundboard.

Plenty of guitarists have developed a style of drumming on their stringed instrument, especially those who have learned with limited accompaniment. They smack out a kick drum rhythm; Not so much plucking the strings as slapping them, striking the bridge with their palm, and then outright hitting the wood.

If all you are after is a solid tone, there is a lot you might miss. Try your mic at the bottom corner of the sound board, as though it were the head of a drum.

Similarly, bowed instruments have an entirely different tone at the strings. My favorite example comes from The Beatles' "Eleanor Rigby," featuring an octet of violins, violas, and cellos. Paul McCartney had wanted this to sound different than the soft and beautiful strings on the song "Yesterday," also recorded that year.

Engineer Geoff Emerick achieved a really harsh and dramatic sound for "Eleanor Rigby," by moving the mics very close to where the players' bows hit the strings. The session players were not happy with this, as the squeaks and minor playing mistakes were magnified, but The Beatles really dug how dramatic it sounded.

Obviously, I'm not telling you to force your technique on the players, as that rarely works in worship and in life. But by essentially just moving the mics to suit the arrangement, the same band produced a totally different sound in the same studio.

Reverberation

Finally, consider the space. This can be a bit more challenging in more of a pop/rock setting, as drums and amps can fill that space, making it hard to get enough isolation.

Consider how the audience is meant to hear acoustic instruments: No one holds their ear six inches from the sound port at a concert. The sound is intended to spread across a stage a little to reach the audience. Consider again "Eleanor Rigby:" The players were uncomfortable, because they trained for years to sound good across the stage, not at the string.

Some great early records were recorded with just a few mics, placed strategically, capturing the whole performance rather than isolated performers.

Putting it All Together

This past Easter, at Crossroads Community Church, we presented a rock band with choir and violin. Finding a way to make the violin sing properly was a bit of a challenge. Placing mics nearby was capturing too much of the drums and amps. When we placed a directional mic at the strings, though, it was a bit harsh.

After a few experiments with different types of mics, our Front of House engineer settled on placing a lapel on the violin. This captured the sound at the performer and provided enough direct signal to be used practically in the mix he was building. The characteristics of the mic also helped reduce the harsh sound.

Some of the coolest recordings I've done had a mic near the guitar's port, another on the neck, and third mic on the stage. All three captured some aspects of the guitar, but blending them really captured the magic. Plus it was easily adjusted to fit the song; If it needs more body, I emphasized the port. For more attack, the mic at the strings was used. For more mellow sounds, the ambient mic was prominent. This created a thin line between the performer and the audience, unencumbered by the technology that drives the sound. That can be so key in a worship context.

Resonance, rhythm and reverberation can help you plan a strategy, but using all three as needed will help you deliver a custom sound for any instrument.

For that matter, keep the DI box and mix that in too! There's a world of possibilities if you take the time to build your sound.

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