Gorgeous & Gratifying Guitar Sounds (Part 3)

By David Franz

Hey folks. Hope you are all enjoying the summer. In this month's column, I'm going to wrap up our guitar production trilogy. We've progressed from getting sweet signals from your guitar into Pro Tools to adding "stereo meat" with doubled tracks and layers. Now it's time to put the finishing touches on your tracks using compression and EQ.

A Lesson In Compression
Subtle nuances in a guitar performance can really be the highlight of a track. But sometimes the other tracks in a mix can obscure these nuances. Enter compression. From delicate acoustic guitar parts to heavy Marshall distortion, compression can help your guitar tracks sound better, and even sit better in a mix.

Knowing how compressors really work can help you achieve the sound you want. In simple terms, compressors turn down the loudest parts of an audio signal, thus reducing the dynamic range of the signal and enabling you to increase the level of the overall signal. Translation: the loudest parts are a little softer and the softer parts are a little louder.

The Usual Suspects
There are five or six main parameters on most compressors: threshold, ratio, attack time, release time, knee, and gain.

The threshold is the volume level at which the compressor starts compressing. The attack time is how fast the compressor reacts once a signal is over the threshold. The knee is how fast the signal reaches full compression once it's over the threshold. The ratio is how much compression is applied to the signal. The release time is how long the compressor stays on after the signal has fallen below the threshold. Compressors also have output gain adjusters to make up for the "lost" gain from the act of compressing.

If a signal comes in beneath the threshold of the compressor, nothing is done to it. Thus, lower volume signals are not touched, except by the output gain adjuster. However, if a signal surpasses the threshold, it is compressed. The nuances are still there, yet there's less dynamic range between the loudest and softest parts of the track. With compression, the quietest bits in your track become easier to hear, while the loudest notes don't stick out as much. Your emotional and inspiring guitar performance will sit better in the mix, and you won't have to ride the volume fader on each expressive note.

Threshold...Ratio...It Sounds so Technical
How do you apply a compressor while recording or mixing? Here's what I do. First I'll listen to the track and decide if it would benefit from compression. (Compression is not always necessary, and can make a track sound worse if it's applied incorrectly!) Then I'll find the threshold at which I want the compressor to kick in. I usually set the threshold in one of two ways:

1. High threshold — This will only lower the peaks. With this setting, the compressor kicks in just on the loudest parts of the track.
2. Low threshold — With this setting, the signal is almost constantly compressed.

I might go back and tweak the threshold later, but first I'll dial in an approximate compression ratio that might be appropriate for the track. How do I decide that? I listen to the track and decide how much I want the lower-volume notes to become more present in the track. If it's just a little bit, I'll use a ratio of 2:1 or 3:1 so that the loud notes only come down a little too. For tracks that need more note leveling, I'll use 4:1 to 6:1...even up to 10:1 to really squash the track and make the volume level very uniform. Consider the math: With a 4:1 ratio, a signal that's 8dB over the threshold will come out of the compressor at 2dB over the threshold.

Attack, Release, and Knee
Next, set the attack and release times. This takes some thought and some listening. The attack time determines how quickly the compressor reacts to a signal that's over the threshold, so consider the type of instrument and part you're compressing, and whether or not you want to compress the initial attack of the instrument. For drums, the attack time is always VERY fast – attack times are often a fraction of a millisecond. However, there are no hard and fast rules for compressing guitars. A short attack time can compress the beginning of a picked or plucked note (which often is the loudest part of a guitar note). But sometimes you'll want the beginning of the note to cut through, so it might work better to set the attack time at around 10-20 milliseconds. The same logic works for bass guitars as well.

The release is just as important as the attack, because it determines how long the compressor stays active once a signal falls below the compressor's threshold. Short release times let the compressor cut out more quickly on notes that fall below the threshold. To make the compressor really work, set the release time to 20ms. For a smoother sound, use values over 100ms.

Knees are pretty easy to understand. A "soft" knee means the compressor takes its time to get to full compression (think "smooth curve"), whereas a "hard" knee setting makes the compressor reach full compression quickly (think "right angle"). Use your judgment in setting this parameter by listening.

What's the Gain?
Often called "makeup" gain, the output gain on a compressor is used to make up for the gain that has been compressed out of the loudest parts of the signal. That is, if a signal comes into the compressor and is reduced by 5dB, you can increase the output gain to add 5dB back to the signal without the loudest parts clipping.

Common Compression Treatments on Guitar
The following graphic shows actual guitar waveforms with three common compression settings: Just peaks, light constant compression, and squashing. (Also consider using compressors and limiters together to enjoy the benefits of both constant compression and a peak limiter...as in this month's Pro Tools session example.)

View Common Compression Graphic.

Keep the Flavor, Drain the Fat
Compression isn't the only tool we can use to make a guitar stand out (or fit better) in a track. Enter the equalizer. Although not really used to "equalize" per se, an equalizer (EQ) alters the frequencies in an audio signal. It allows you to emphasize or de-emphasize specific frequencies – brightening the tone of an acoustic guitar, for example, or reining in an overly boomy bass. We often need to creatively use EQ to clarify and separate sounds in a mix, especially when we thicken our guitar tracks with distortion and/or "stereo meat" (see last month's column).

Guitars can produce a very wide range of frequencies. Without fail, some of these frequencies will overlap the frequency ranges of other instruments in a mix. Boosting and cutting certain frequencies on particular instruments can improve this frequency interaction by giving each instrument its own space in a mix. In other words, we need to carve holes for each instrument and slice the stereo meat.

Carving Holes
The most basic thing to remember is that it doesn't matter how good an individual track sounds by itself — it's how the track fits into the mix with all the other tracks. Thus, it's essentially pointless to solo a track and EQ it. Instead, think about how you want to alter the track and then add EQ while listening to it as part of the full mix. Don't know what frequency to boost or cut? Use adjectives to describe the sound you want. The following chart will help.

Find the frequency range you want to alter, boost the gain of the EQ up to its max, and then fine-tune your search by sweeping through the frequency range. Then lower the gain to boost or cut the frequency at the right level.

Common EQ Treatments on Guitar

Here are some common EQ treatments that I use on guitars:

1. Bass Frequencies — Depending on the song, I might cut a good chunk of the low bass frequencies (below 100Hz) to let the bass instruments have free reign over that range. Other times, I might boost a little 100Hz to warm up a track and give it more power.
2. Mid Bass — "Mud" lives at around 300-350Hz, so I might cut some here too.
3. Midrange — I often boost a little here to give the guitar its own space, safely between the bass and the vocals, and make it more beefy.
4. Upper Mids — This is the most important area to get "right." Guitars and vocals occupy a good chunk of this frequency range, so I usually try to cut some of the guitar between 1-4kHz to open up a hole for the vocals. Then I might boost the 4-5kHz range to fit the guitar around the vocals and give it some more presence in the mix. 3kHz is a good frequency to give guitars more "bite," if it doesn't interfere with the über-important vocals.
5. Highs — If needed, I might add some brightness to the guitars at around 8kHz or 10kHz.

Here's one EQ setting that demonstrates some of these techniques.

In this Pro Tools session, I've used compression, limiting, and EQ to alter the sound of a guitar track. I arrived at this sound after listening and tweaking the track in relation to the other instruments in the song. By themselves, the guitars might not sound like the best guitars you've ever heard — but they work really well in the overall mix.

Wrap Up
EQ and compression are two invaluable tools for perfecting your guitar sound. I encourage you to experiment with these tools and techniques (as well as adding reverb, delay, and other creative effects) to take your guitar sounds to new levels in Pro Tools. Join me next month when I'll cover techniques for making great drum tracks with samples. See you soon. Peace.

Like what you see in this column? Check out my book Producing in the Home Studio with Pro Tools (2nd Edition). You can buy it online right here through Digidesign's web site, or visit www.protoolsbook.com. Interested in personal instruction on Pro Tools from yours truly? Visit www.berkleemusic.com and learn about several amazing Pro Tools learning experiences available online though Berklee College of Music. Interested in hearing my band? Visit www.lipfloater.com. Wanna see my studio and hear some samples of my work? Visit www.undergroundsun.com and/or www.davidfranz.com.

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