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Tracking in the Unplugged World

Practical strategies for recording acoustic ensembles.

By Myles Boisen

Excerpted from Electronic Musician, November 2003

Trends in recording come and go, but acoustic music is a constant that can be relied on to sustain and challenge all engineers. From miking to mixing, successfully capturing an acoustic ensemble in the studio always puts one''s engineering skills to the test.

Having engineered a wide range of acoustic groups, I can say that the techniques necessary for a successful outcome can vary greatly from project to project, based on factors such as musical style, group composition, and budget. I''ll delve into specific examples of certain projects that I''ve worked on, which will show a variety of engineering approaches. But first I''ll give an overview of some of the key issues and challenges you''ll face in almost any acoustic-recording situation.

Getting Comfortable

When setting up for an acoustic session, my first concern is always for the comfort and relaxation of the players. Most acoustic musicians need to play near to each other, so that they can hear and see subtle musical cues and can feel supported by and involved with the ensemble. Engineers, on the other hand, prefer to separate sound sources in order to retain maximum control over the individual instruments in the mix.

After more than 20 years of recording, I''ve learned that putting the musicians'' needs first always increases my chances of capturing an inspired, connected performance. Certainly, technical compromises may result, but ultimately there is no point in pushing for a technically “perfect” recording that ends up feeling stiff or unmusical. I like to start with a tight circular arrangement in an acoustically appropriate room. My objective is to create an environment that is as similar to an informal living-room jam session as possible.

With this goal in mind, I don''t automatically make musicians play with headphones on sessions of this type.

My experience has shown that musicianship thrives when the musicians in an acoustic ensemble find their comfort zone and play at an appropriate level for the room. More often than not, the elusive qualities of blend, acoustic balance, and solo volume go out the window when a group disconnects from the room and becomes dependent on headphone monitoring.

On the other hand, if hearing problems in the studio can''t be solved acoustically—by repositioning performers, changing the room''s characteristics, or suggesting a different playing dynamic—I''ll gladly hand out headphones to anyone who wants them. For example, a kit drummer or percussionist will rarely be able to hear an unamplified acoustic bassist or guitarist clearly in the controlled acoustics of my studio. In that case, headphones will enhance the recording by allowing the drummer to play at his or her desired performance volume.

Using quality microphones and giving careful attention to placement are essential in a tracking session, especially when recording natural acoustic sounds. Besides capturing accurate, pleasing sounds on the intended instruments, it''s important to consider how every mic on an acoustic session deals with off-axis sound, also known as bleed or leakage. Typically, there will be noticeable coloration in the timbre of signals picked up at the sides and rear of a unidirectional microphone, and this is a particularly crucial factor when you have a number of instruments in the same room.

Style Conscious

Acoustic ensembles come in many sizes and varieties, and you have to adjust your technique to fit the style and vibe of a given group. For example, a mandolin-guitar-bass lineup performing old-time music in the style of the popular O Brother Where Art Thou soundtrack will need to be tracked and mixed differently than the same combo recording high-tech “new-acoustic” music or modern bluegrass. Similarly, the production values of a singer-songwriter combo will vary drastically depending on whether they are aiming for pop-radio airplay or pursuing careers as Chicago-blues revivalists.

I''ve found that in general, older genres require special attention to minimalist miking techniques and capturing a good overall blend. Conversely, contemporary acoustic-music styles may rely heavily on overdubbing, separation, effects, and other production values that are standard practice in the rock world. Therefore, the best advice I can give as far as recording a specific group is to do your homework and listen to some recorded examples before venturing into unfamiliar production territory.

To Punch or Not to Punch

When recording any live ensemble, questions about fixing parts will inevitably arise. In the case of acoustic groups, there is no set answer that an engineer can give, especially when recording everyone in the same room. If the question is “Can I rerecord that solo?” it is useful to remind the group that, because of the leakage that is inherent in the situation, it will likely be faster to record a fresh take of the entire song with the whole group, rather than to punch-in a replacement solo. For something such as a missed guitar chord, bass note, or clarinet squeak, my answer is usually, “I''ll try.”

It''s most efficient to do a punch-in fix immediately after a take, before the musicians change their mic positions. That way, if a recorded “ghost” of the mistake is still audible on other tracks or if the punch-in or punch-out doesn''t work, the group will be most amenable to doing another take right away. Taking detailed notes about mic selection, placement, preamps, and so on will also make it possible to attempt fixes at a later date, when you can focus your concentration on repairing flaws in an otherwise satisfactory take.

Overdubbing is often a great way to deal with vocals, solos, and tricky passages that might otherwise slow the momentum of an ensemble date. Scratch tracks of the aforementioned can be performed and recorded along with the ensemble, as long as the musician in question is acoustically isolated. But normally that entails everyone using headphones, which can make players hypercritical or can skew the group dynamics. In my experience, it is always best to persuade players in this situation to slip one headphone cup off their ear, so that at least half of their hearing is trained on the balance in the room.

When it comes time to overdub replacement tracks or to add entirely new musical layers onto an acoustic music production, don''t forget about the importance of ambience. It can be distracting to hear a natural, roomy ensemble with one foreground vocal or instrument that is obviously overlaid or isolated in a different (usually deader) room.

If your intent is to obtain a unified blend of all the mix elements, make your overdub merge into the whole using mic placement rather than added effects. Record the overdub in the same space that the ensemble used, rather than in an iso booth. And don''t be afraid to add extra room sound to the track by using a more distant mic position, using an omnidirectional or bidirectional (figure-8) mic, or recording a second room mic. If you can get the track to fit in with the overall ambience right off the bat, that''s one less challenge during mixdown.

For those musicians who are working alone or who are layering many instruments one by one, similar principles can be used to create a colorful ensemble sound on a track-by-track basis. Incorporate a room ambience you like into your foundation track—be it percussion, acoustic guitar, or whatever—and make it a point to match or complement that room sound on each successive overdub.

Again, using a separate room mic for each track is an effective technique that allows for many creative possibilities in the mix. Excellent examples of this approach can be heard in the recent records of Tom Waits. When working as a session guitarist on Waits''s Blood Money (Anti Records, 2002), I was delighted to find that my guitar, mandolin, and banjo parts were being picked up simultaneously by any combination of mics set up around the room, including an old boom box that was wired directly into the console.

Stanch the Bleeding

In live-ensemble recording scenarios, leakage is frequently a fact of life. It''s always best to deal with excessive bleed at the source, by using proper mic placement and pickup pattern control. Getting a tight, focused sound when tracking guarantees that when you''re mixing, raising a single fader will boost the desired instrument without distorting or washing out any other source in the room.

After mixing a few acoustic sessions, the ear begins to discriminate between good bleed (which adds depth, liveness, and richness of tone to the ensemble) and bad bleed (which is usually a concentration of muddy midrange frequencies, indistinct bass, or phasey high end).

The most important rules in this regard are (1) don''t automatically reach for the EQ control just because you hear leakage on a track, and (2) don''t make leakage even worse by adding too much compression.

If you feel relatively confident that your tracks and overall ensemble character are in the desired ballpark, I recommend that you start your mix by listening to all the tracks together without EQ or effects. That will help you to avoid the common mistake of analyzing and tweaking each track separately—a common practice that can work to the detriment of overall warmth and clarity. Once you have the ensemble sound established, it will be easier to evaluate and refine the effect of EQ and bleed characteristics in your mix by muting tracks one by one, rather than listening to individual channels isolated from the whole.

Recording Singing Guitarists

FIG. A: One successful method for miking a singing guitarist involves using an omnidirectional mic placed close to the bridge or sound hole. The vocal mic is positioned slightly above and off to the side of the singer's mouth.

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Sooner or later, anyone who records acoustic music has to deal with the challenge of recording a vocalist who plays acoustic guitar. For tracking purposes, seasoned musicians are usually able to overdub to a scratch guitar or vocal track. There are those instances, however, in which the performer''s needs—perhaps influenced by inexperience or irregular timing—dictate that the vocal and guitar tracks be recorded simultaneously. On such occasions, it is good to have a few miking tricks up your sleeve.

Although it is possible to mic a singing guitarist with a single microphone, let''s start this discussion with a minimal two-mic setup. As always, leakage and phase cancellation between the two sound sources is a crucial factor. Most engineers have dealt with this common problem before. Typically, the vocal or guitar will sound fine alone. But once the second mic is brought into the mix, unpredictable tonal distortion dominates the sound, changing as the faders are moved.

To minimize those problems, start by miking the guitar using either an omnidirectional mic by the bridge or sound hole, or a figure-8 mic in front of the neck joint aimed at the sound hole, with the off-axis side or “null” of the pickup pattern carefully oriented at the singer''s mouth. In an acoustically dead room, the figure-8 guitar mic should do a very good job of rejecting vocal sound, especially with a quiet vocalist. Conversely, the omni mic will not reject much vocal sound, but since it has no proximity effect, it can be placed very close to the guitar without boominess.

To pick up the vocals, start by using your favorite vocal mic, positioned a bit higher and farther away from the mouth than usual (see Fig. A). Trying to get the vocalist to sing with his or her chin up toward the mic, and head turned somewhat to the left (for a right-handed guitarist). Such placement increases the distance between the two mics, and prevents the singer from projecting toward the guitar mic. When placed properly, the vocal mic will add sparkly guitar harmonics to the mix, and midrange boxiness from the guitar will be minimal.

If you want a more elaborate setup, try using a pickup-equipped acoustic and recording its output to supplement the signal picked up by the guitar mic. Or try replacing the omni or figure-8 guitar mic with a pair of cardioids in an XY configuration. With such a pair, you''ll need to experiment in order to maximize rejection of the voice.

Upright Advice

FIG. B: A good way to mic an upright bass so that you obtain minimum bleed is to wrap the mic in a towel or a piece of foam and wedge it in the tailpiece of the bass.

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Here''s a trick to increase separation when recording the acoustic bass, particularly in a jazz or a rock setting and with a drum kit. Select a dynamic mic that has good low-end response (my favorite is the Sennheiser MD 441 because of its supercardioid pattern and onboard EQ), wrap it in a towel or a piece of foam being careful not to block the mic''s grille or acoustic vents, and wedge it in the tailpiece of the bass.

The mic should be pointing up and positioned with its diaphragm just below the opening between the legs of the bridge (see Fig. B). This ingenious technique, which was shared by veteran German bassist Peter Kowald during his recording with Damon Smith of the bass-duo CD Mirrors—Broken But No Dust (Balance Point Acoustics, 2001), yields the most favorable ratio of bass to room sound. In addition, the bassist can move freely without any change in timbre or level.

Myles Boisenis a guitarist, producer, composer, and head engineer/instructor at Guerrilla Recording and The Headless Buddha Mastering Lab in Oakland, California. He can be reached at mylesaudio@aol.com.