The Music Espionage

Acoustic Guitar


Because the acoustic guitar is such a versatile and adaptable instrument and performed with such a wide range of methods; when it comes to post-production and mixing there are a number of things to look out for. You may be dealing with a nylon stringed flamenco wonder, a pick strummed rock ballad or even an eccentric tapping rhythm, played on the guitar’s body. These will all have very different characteristics, with many elements that are spread across the audio frequency spectrum.
Your average acoustic guitar track will not be sequenced or modeled using digital software. So you will be dealing with physical audio, recorded either through a direct input or more commonly carefully placed microphones. The advantage of this approach is that the neck microphone produces a bright, detailed sound with very little bass end, and will cause less low-frequency phase cancellation if the track is ever played in mono. You will also have a number of other tracks, recorded from around the body. Most preferred are an ambient/room response, normally pointing at the sound hole and the extremely popular ‘sweet-spot’ microphone. This being a microphone placed about 3 inches from the 12th fret pointing back towards the body. Having different tonalities at either side of the stereo image can provide a wider, more interesting stereo image and allow you to mix these

EQ and Frequencies:
The majority of time spent mixing acoustic guitar will be dialing in the EQ. Like any mixing there is no magic trick to it, no preset that works every time. The playing style, the key of the song, the pick size, the string gauge and what instruments it will play with, are all factors that create a completely unique guitar part that needs to be equalized differently.

Acoustic guitars put out loads of bass frequencies. To prove it, take a low-pass filter and sweep it all the way down to 100 Hz, listening to everything below 100 Hz.

Hear a bunch of rumble? Thought you would.

There may be the occasional acoustic singer-songwriter track that calls for this low frequency information, but the majority of the time you need to get rid of it. How much you roll off is a matter of listening. Some acoustic tracks roll off at 150 Hz. Others roll off as high as 400 Hz. Even if you only roll off 100 Hz and below you will still be removing a lot of unwanted frequencies and greatly clean your mix. The 150-300 Hz range can be used to beef-up the tone of the guitar, but it can be add muddiness, so only boost frequencies in this area if it clearly improves the sound.

The majority of the presence is placed from the low mid, up into the high. The 300-600 Hz range can be boosted if you have a thin sounding guitar. The 600-800 Hz range is your meaty mid-range sound. Cut this if necessary to give better tone and better distinguish from other instruments. Jumping to the 1-3.5 kHz range, these frequencies can push the guitar to the front of the sound mix and effect note definition. Boost these frequencies when looking at fingerpicking-style guitar and guitar riffs. Finally, you may want to add some sparkle to your acoustic guitar. A gentle high frequency shelf can be great for this. Boost it just a little at a time until you achieve just the right amount of “air” without allowing the track to become harsh. The 3.5 kHz to 12 kHz range is all about this “sparkle”. This range adds brilliance and can make the guitar jump out.

If recorded accurately, with time and effort spent on microphone placement, a guitar sounds great even without equalization. But when you place that same instrument in a realm with other instruments such as the piano, bass, and vocals, equalization is very important to not just bring out the best in the instrument, but to correctly blend and set it with these other instruments.

Dynamic Shaping:
In a standard rock/pop ballad the acoustic guitar will normally stay static throughout, with few jumps in the level during the song. The same can be said for more classic nylon string styles. Because of this, often compression and other forms of dynamic manipulating are academic and simply not needed. But because the acoustic is so versatile you may be mixing a more percussive style, where there are moments of sudden jumps in volume and would benefit from compression to even out the performance

Here are my 3 main reasons to compress acoustic guitar:

1. Control Dynamic range – You may want to simply iron out the performance. Even the best of musicians will not play every note with the same velocity, meaning you get the odd moment the level pops or jolts. Careful control of your ratio and threshold will monitor this and balance the range.

2. Louder transients – Generally speaking, the sound of the pick or even finger on the strings is usually pretty quiet in comparison to the overall volume of the guitar. In some songs, however, bringing out that pick/finger noise can give the guitar a more percussive sound. By compressing the guitar, you can achieve a very choppy, rhythmic tone. When the pick hits the strings, there is a lot of high-frequency information there; compressing this will accent those high frequencies. Nevertheless, if you are thinking of compressing or limiting because you have a few moments where the level jumps, for what ever reason that maybe. You may be better off simply recording the track again or overdubbing at that moment. It will absolutely taken more time, but your sexy sounding mix will thank you for it.

3. More harmonic content – Acoustic guitars, like pianos, are chock full of harmonics. When you play a single note on the guitar, you hear a few more “ghost” notes ringing out in the higher registers. These are harmonics, or harmonic frequencies. Obviously, the more notes you play, the more harmonic content you will hear. This is what can make an acoustic guitar sound full. In a mix, though, the harmonics may simply be too quiet to hear, and lost. With a little compression, you can bring them to a level where they can still be heard over the other instruments in the mix.

4. More sustain – Just like an electric guitarist uses a compressor pedal to increase sustain, so will using a compressor on an acoustic guitar. Since compression turns up the quieter parts, you will hear the notes ring out longer, giving the illusion of more sustain.

 Think it through! While compression has its benefits, it also tends to bring up the amount of room noise in the track. In a pro-studio this is not a big deal. In a home studio, however, where you have a computer and hard drives whirring in the background, too much compression could make for a noisy track.

– Example of clean, no FXs acoustic guitar:

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– Example of acoustic with slight compression

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Applying Effects:
Though it may not be common to add compression onto the most basic acoustic guitar tracks, additional tonal effects are! But think of this, if you have a well-recorded track that has been carefully balanced and equalized, do you really need FXs. Will it add anything to the mix?

Below are some of the most common that will nicely round off the sound and usually add better definition.

Reverb may be needed if the recording was made in a small room or studio, close-miked or where DI signals dominate the recorded sound. Mono recording can also be given a sense of space and width by adding a little stereo reverb. Ambience settings with pronounced early reflections are particularly effective in adding life and sparkle to acoustic guitar, though plate and room settings can be used as an alternative where you want a more obviously spacious sound. The main objective is to get a well-balanced tone with enough ambience or reverb to match up the guitar sound with the rest of the mix.

– Example acoustic with slight reverb

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Delay and Phase effects, the most common being Chorus for the acoustic. Chorus can range from a subtle effect that adds a shimmer to your guitar to a more dramatic sounds that utterly alter the timbre. Chorus effects work by creating a very short delay that varies with time. A chorus is tone modification device that doubles the incoming sound and plays it back simultaneously slightly, but not unpleasantly, out of tune. This gives a guitar a doubling effect, somewhat like a 12-string guitar. Most chorus effects have at least two controls: one that varies the speed of the effect and the depth. Faster speeds combined with greater depths will create a warbling sound, like a Leslie speaker on an organ, while slow speeds and shallower depths add a subtle sense of motion to your sound. When used in moderation, chorus can add a sense of energy to your sound, mimicking some of the natural acoustic properties of the instrument that tend to get lost in the direct pickup sound.

– Example acoustic – Chorus – High Depth and High Rate

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– Example acoustic – Chorus – Low Depth and Low Rate

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