Producing Acoustic Guitar
Prouding the Acoustic Guitar
The acoustic guitar is still very much in style these days, used in the
many genres of folk, pop and rock music. While the acoustic guitar
remains one of the most simplest instruments, it also remains one of
the trickiest to get a superb sound on in the studio. It's really not that
challenging to record, as long as you follow a few basic guidelines.
The sound you obtain has a great deal to do with the competence of
the player; the superior the player the better the sound! The best
players will play a guitar that will costs thousands of dollars and are
hand made by a guitar luthier.
If you are the player, first choose an appropriate type and gauge of
string for the type of sound you desire and make sure that the guitar's
action is set up correctly so that it plays in tune and without buzzing.
Make sure the intonation is set up so the guitar plays in tune in any
position on the neck. There are many different types of steel-cored
wound string, all of which have slightly different properties. The most
commonly used types on acoustic guitars are bronze, phosphor
bronze and ocassionally nickel wound. An instrument with lighter
gauge strings (11 to 53 ) will generally be easier to play, but the
sound will be thinner and lower in volume and buzz a lot on the frets.
On the other hand, very heavy strings (a set beginning with a 14gauge high E) can sometimes sound bottom heavy and lacking in
higher overtones on the wound strings. The best situation is usually
the thickest set of strings that are comfortable enough for the guitarist
to play. Start with medium gauge strings which will give you a very
decent sound to start with (13 to 56).
The size of the acoustic guitar has a lot to do with the frequency
range that it projects. The bigger the guitar, the more low end will be
generated. These guitars are most effective with strumming chords in
the open chord position often associated with country and folk music.
These “jumbo” guitars are normally strung with medium to heavy
gauge strings that are capable of producing more resonance due to
the larger amount of wood that will resonate sympathetically. A
medium size guitar will sound tighter and project the sound more
quickly, which makes it great for soloing.
There is also the nylon-string guitar or better known as the classical
guitar where the top three strings are made of nylon. This type of
guitar produces a mellow and warm sound. It obviously does not
generate the same amount of mid-range and high frequencies that
steel-string guitars project. Nylon guitars are becoming more popular
in pop music due to their capability to produce harmonic content in a
frequency range that will not negatively affect the presence of the
lead vocal sound. A great example of this is in the music of “Sting”. In
a song like “Fields Of Gold” the nylon guitar can be mixed tighter to
the lead vocal for it is not encroaching in the presence frequency
range of the lead vocal sound. If “Sting” were to use a steel-string
guitar instead, he would have to lower the overall level of the guitar
because the high frequencies produced by the steel-string guitar
would compromise the lead vocal presence (5Khz-12khz).
When a recording situation like this occurs, you would then have to
lower the level of the guitar, where it would then distintctly separate
the vocal’s melodic content sound from the harmonic accompaniment
provided by the guitar, which is not desirable for pop music.
The 12-string guitar is the grand piano of the acoustic guitar family.
Usually played in a strumming fashion with a light-medium pick and
with chords in open positions. The 12-string guitar works most
effectively by itself or with little accompaniment for it takes up a lot of
the frequency bandwidth in the musical range. If you already have a
basic 6-string performance and you feel you need an additional
brighter guitar sound, overdub the same guitar but change the G and
D strings with lighter gauge strings and tune them up an octave
(Nashville tuning). The Nashville tuned acoustic guitar is a lot easier
to play than a 12 string.
If the guitarist is using a pick, it is always worth trying various picks of
different thicknesses. With strumming you will tend to get a more
even sound with a medium to light gauge pick. A light-medium pick is
suggested if your production needs mainly a rhythmic performance
instead of a melodic dynamic performance. With soloing, a thick or
medium gauge pick works best for incorporating dynamics and
producing a melodic/rhythmic idea .
Another thing to consider is that the sound of acoustic guitar will
depend a great deal on the environment in which the instrument is
recorded in. Acoustic guitars thrive in live sounding studios, where
early reflections and reverb time, can elongate the musical tonality of
the guitar and create a sense of dimension. While artificial reverb can
be used to revitalize the sound of a dead room, getting a realistic
natural sound always produces better results, and if necessary, you
can later add artificial reverb. To get a more live sound out of your
room, try to position the guitarist so that the instrument is played
close to reflective surfaces like hard floors, doors and solid furniture.
If there is carpeting on the floor of your recording room try placing a
sheet of plywood on the floor and get the guitar player the take off
his/her shoes. Be prepared to have an additional pair of socks in case
of gross air pollution.
Most studios should have a broad range of microphones to choose
from, however there are very few dynamic microphones capable of
doing justice to the acoustic guitar. Dynamic microphones will work if
it is a live show for they are cardiod in their pickup pattern which can
better control feedback.
It is best to use a condenser microphone(s) for its greater highfrequency accuracy, and usually ones with an omni polar pattern for a
more of an even frequency response and not prone to proximity
effect. If the stuio/room is too live sounding you might need to use a
cardioid pattern to minimize the ambience, but remember to not
compromise the overall quality of the guitar sound from adding
potentially poor sounding characteristics of the studio/room.
Capturing a natural sonic balance from the guitar is incredibly
valuable. There are different sounds coming from different places on
the guitar that are important in contributing to an overall realistic
natural sound. If a microphone is used too close to the guitar, the
direct sound from that part of the guitar will dominate the sound over
other parts of the instrument and not capture any ambience. You risk
picking up only a part of the instrument when what you're really after
is an overall holistic sound of the entire guitar. The opposite can
occur if your microphone is too far away from the guitar, where you
end up with a lot of room ambience, leaving the original sound distant
and unfocused.
As for the specifics of microhone placement, position your ear as if it
were the microphone while somebody else is playing the guitar. Move
your ear around to find the "sweet spot". A common approach is to
set up the microhone around “6in-8in” from the guitar, with the
capsule aimed between the sound hole and where the neck joins the
body (14th fret). This will usually produce an overall well integrated
sound. The levels of direct and ambient reflected sound will be about
right and the sound hole's contribution will be managable for the
microphone doesn't point directly at it. If you need more low
frequency content, move the microphone position closer to the sound
hole. If you need a brighter sound move the microphone closer to the
12th fret. This is where the first series of harmonic overtones originate
that contribute more high-frequency content to the overall guitar
sound.
If you have a pair of enclosed headphones that are very accurate to a
reference point that you have established, you can easily experiment
with tweaking the microhone placement while listening for the best
pickup position in your headphones.
If you find an inspiring sound in this manner, remember to check the
sound quality on your monitors before committing yourself to
recording. If you find a good position but feel the sound is too dead,
try switching the pattern to omni and if the opposite occurs where the
guitar sounds too ambient, switch the omni pattern to cardioid. If you
are working with a professional studio musician they will most likely
have a custom-made guitar. Ask them where the “sweet-spot” is on
their guitar for the performance you require.
Finding the Sweet Spot with One Microphone
If the guitar player is soloing and moving up and fown the neck try
placing the microphone closer to the sound hole to acheive a fuller
sound from the guitar. This will compensate for the lack of low-end
that the guitar generates when used in a soloing fashion.
Most players will use a medium to heavy thick pick to solo with.
A guitar with a built-in pickup used along with a microphone will
undoubtedly generate a decent sound but could generate phase
problems between the timing of the pickup signal and the microphone
signal. Experiment with moving the mic closer and further away from
the guitar. This will affect the phase relationship of the two sound
sources. Another approach is to sync the waveforms of the
microphone and the direct pickup sound by readjusting one of the
waveforms in Pro-Tools by a few samples or milliseconds. Since the
player is most likely listening to the microphone pick up, it might be
best to delay the D.I. sound until the two waveforms sync up and are
in phase. If you do plan to use both signals in the mix, have the
player first tap the body of the guitar in order to produce a transient
with his pick before you start recording. By doing this, it will be much
easier to sync up the two waveforms because you have a transient
waveforms to sync with.
If you are cutting a track in a studio with drums try using the direct
pickup only and replace the performance with an microphone pickup
later in an overdubbing session. If you chose to use the bed track
acoustic then use both signals and try to get the natural sounding
high end from the microphone and the body of the sound from the
direct pickup. Even though direct pickups on acoustic guitars have
come a long way in quality, I have yet to discover one that sounds as
good as a fantastic microphone pickup.
Stereo Microphone Pickup
Stereo miking works well for some situations where the acoustic
guitar’s sound quality will be playing a major role in the final
production. The Coincident “X-Y” technique is good but I feel it still
falls short due to its lack of direct “on axis” sound in capturing the
very top end of the the acoustic. It will provide you with more of a
large cardioid pickup sound but with less high-end than you would get
with a single microphone pointed directly on axis.
Make sure both mics are Identical pencil condensers, the same
model and positioned the same distance from the guitar. The stereo
“Rode NT4” microphone is very affordable for this application.
The legendary acoustic guitarist “Don Ross” uses the NT4 and
usually adds a little top end to both channels equally.
Coincidental (X-Y) Microphone Technique
Some engineers will start with a stereo pickup with two microphines
where one microphone will be positioned at the 12th fret and the other
microphone over the saddle. This provides an etremely wide stereo
pickup and is a suitable starting point. Some engineers will start there
and slowly move both microphones in towards the sound hole to
capture an ideal sound. I usually start with placing a microphone
over the 14th fret and another just slightly off-centre from the sound
hole, giving me control of the various sounds produced by the guitar
and a decent stereo sound. The stereo sound will depend on how far
you pan the two microphones in your mix, and because we live in
digital delivery system, you don’t really need to worry about any
phasing problems that often occurred when vynyl records were
mastered.
Starting Point for Stereo Microphone Pickup
As with any studio recording, the makeup of the cue mix you feed to
the guitarist will be extremely important, so be prepared to take a little
time in preparing the headphone mix given the sensitivity of the
microphones customarily used in acoustic guitar recording, for it's
easy to pick up annoying leakage from the headphones. Solo the
microphone(s) to check for leakage and if there's a lot of leakage
coming through (from a click track, in particular) then consider turning
down the overall headphone mix level or using a different pair of
headphones. Closed headphone models are obviously best in this
application and also reduce the possibility of feedback.
Recording acoustic guitar will usually benefit from a little processing.
This should be kept to a minimum while recording, so that you leave
your options open for the mix, it's always safer to leave EQ and
dynamic processing until the mixing stage.
Equalization
Equalization of the acoustic guitar is very common but should be
used subtly. The first thing to do is roll off some “boominess” bass
that can occur with a condenser mic set to cardiod pickup. This will
also prevent the compressor from working inaccurately and
maintaining an even harmonic balance for further processsing.
Rolloing off low end can make a big difference in your production; for
example, if other instruments in a pop/rock production have strong
low mid-range or low frequency content, the acoustic guitar’s
prouduction role might benefit if you you lower the amplitude of the
low low end up to as high as 200hz and focus more on the musical
and higher harmonic content of the acoustic guitar.
Most acoustic guitars performing in a strumming or finger picking
style can use a mid-range and/or high frequency boost to enhance
the rhythmic idea of the performance. With high mid-range use a wide
Q (0.8) centred between 5khz-10khz. Try to avoid the low mid-range
area of 2khz-5khz, for this is the mid-range area of electric guitars
that you might need to enhance especially if an electric guitar is
providing a rhythmic idea. If the production can afford to have an
acoustic guitar play a major role in the production, the frequency
presence area of the high-end can be boosted, with an EQ shelving
boost starting from 8khz-10khz, which will produce a silky top-end
sound. If you need musical body and tonality of the harmonic
fundamentals, boost in the 300hz-800hz range with a medium to
narrow Q. With acoustic solos you might need to enhance the low
end between 100hz-200hz to add more body to the performance
especially if the guitarist is soloing high up on the neck.
There will be situations where open chords are performed where the
low end is not consistently even with the rest of the higher frequency
content of the guitar. For example going from a Gmaj to an Emin
chord often produces more low end on the Emin chord because of
the open low E string. This is where a multiband compressor is useful
where the compressor can focus only on compressing and evening
out the low end of the guitar, especially if it is a jumbo sized guitar
with heavy gauge strings.
Compression
With compression for a strumming guitar, a ratio of 3:1 – 4:1, a
medium attack and medium release time should be applied. What
you’re trying to do is even out the dynamics of the harmonic content
of the chord changes without effecting the rhythmic idea.
The transient sound of strumming identifies the rhythmic part of the
performance, so allow the transient nature of the sound to pass
through the compressor unaffected through the application of a slow
attack time.
If the attack time is too quick it might create the illusion that the guitar
player is playing behind the beat and also reduce the rhythmic idea
the player is trying to project. With a little mid-range EQ with this type
of compression, you will establish that the guitar performance as
rhythmic in nature. If you wanted the guitar as a musical part,
compress with very fast attack and release times, lessen the midrange and boost in the 200hz-800hz range. With these settings, the
dynamics will be evened out and the harmonic idea will be more
pronounced than the rhythmic idea. For soloing you might need to
limit the transients slightly and EQ for presence/musical content.
Compress with fast attack time and fast-medium release times to
control the dynamics of the melodic idea. Remember not to over do it
with dynamic processing on lead parts for it needs to still project a
dynamic musical idea.
Creating Dimension
If the guitar performance is continuous strumming, there will most
likely be no need for reverb. Reverb may be needed if the recording
was made in a small room or dead studio to create a live sounding
environment where the reverb time should be set with a decay time of
less than 1.0sec. A mono recording can also be given a sense of
space and width by adding stereo reverb. Ambience settings with
pronounced early reflections are particularly effective in adding life
and realism to a dead sounding acoustic guitar.
With strumming use a short pre-delay of 20ms-30ms and a reverb set
with a 1.0sec decay time. You want to keep the reverb time short so
the performance does not become harmonically confusing sounding.
With a guitar solo use a pre-delay of 60ms-100ms with a warm reverb
using a duller sounding decay time of between 2.0sec-3.0 sec. With
longer reverb times you will elongate the melodic idea of the
perormance. With longer pre-delay settings you can create a more
intimate sound occurring in a nice sounding environment. For a
soloing performance the concept of applying smooth reverb would be
similar to using the sustain pedal on a piano.
If the performance is very fast, use reverb subtly, and if the
performance is slow and melodic use the reverb to elongate a
melodic idea. De-ess the send to the reverb if there is a lot of high
squeaks and finger noise coming from the guitar.
Extra
The Parts of an Acoustic Guitar
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