Lead Tone 1: Basics of Guitar Tone

This is the first in a series of posts which examine, in detail, the basis of lead guitar tone. This introduction covers the basics of frequency response, distortion and dynamics.


Frequency Response

The guitar is a mid-range instrument, which is the most sensitive part of human hearing – so it is little wonder that we guitarists are so fussy with our tone. The guitar itself (i.e. the wood) resonates strongest in the mid frequencies, also the pickups have an electrical resonance that emphasises the mid frequencies even more. Generally speaking, humbuckers will have a stronger mid-emphasis than single coils.

In contrast, guitar amplifiers are very lacking in the mids – guitar amplifiers are ‘scooped’. This is one of the reasons why electric-acoustic guitars sound so unnatural when amplified through conventional guitar amps (electric-acoustic guitars require specific ‘acoustic’ amps). Turning the ‘high’ and ‘bass’ knobs all the way down, and the ‘mid’ knob all the way up, will give you a fairly ‘flat’ response and a rough impression of the actual guitar sound without the mid scoop of the amp.

The last aspect of a basic lead setup is the speaker cone(s). These typically have very limited upper frequency response. Amp cabinets with ‘full-range’ speaker systems would sound incredibly harsh and/or fizzy, so guitar speakers are deliberately made to be ‘lo-fi’ (low-fidelity).

These various cuts and boosts at different frequency areas can all affect the final guitar tone in good and bad ways. Swapping in a wider-bandwidth speaker, for instance, may increase clarity and ‘bite’ but could also increase harshness and fizz. Dropping the mids on the tone-stack might ‘smooth’ out the sound, but could also cause your tone to lose its impact, power or ‘balls’.

Distortion

The three parts of the signal chain described above (guitar/pickups, amplifier, speakers) also introduce harmonic distortion. Usually just called distortion, or overdrive, harmonic distortion is a non-linear compression of an audio signal. This means distortion introduces overtones/harmonics into the signal that were not already there. In short, pickups, amplifiers and speakers add upper frequency content to the signal.

It is important to understand that this is not the same as simply boosting the higher frequencies, such as turning up the ‘high’ knob on the tone controls. This is not boosting audio that was already present in the signal, but is actually changing (i.e. distorting) the signal so that the audio coming out is harmonically different from the audio that went in.

Although everybody is familiar with the distortion available with the ‘gain’ knob on the amp, many people don’t realise that pickups and speakers distort as well. Wide-bandwidth pickups (such as active pickups) sound very clean (some people even describe them as ‘sterile’). By contrast, a P-90 will have a much more complex tone, partly as a result of extra harmonic content. Also, a P-90 has a far more ‘middy’ and ‘peaky’ response while an active pickup has a much flatter response, so this also contributes to the sonic differences between the two.

Also, it is common for people to talk about pickups as being ‘dynamic’ or ‘compressed’. It is usually the case that the more ‘compressed’ the pickup is, the more distortion it introduces. Similarly, a more ‘open’ or dynamic pickup will usually impart less distortion.

Speakers also distort, especially when driven hard. Usually this means very high volumes, though guitar speaker manufacturers may deliberately make speakers which will distort at lower volumes.

Basic guitar tone is a result of controlling distortion and controlling the overall frequency response of the signal along the chain.

But What If I Don’t Use Distortion?

Even guitarists who play with a ‘clean’ sound usually have some distortion – it’s just very subtle, and often imperceptible. It is usually a subtle, controlled use of distortion that makes a clean sparkly tone, rich and complex rather than dull, lifeless and sterile. Remember, harmonic distortion is simply harmonic content that was not originally present in the signal. That does not mean that distortion needs to be ‘in-your-face-high-gain’ type distortion. You can use subtle distortion to ‘warm up’ and thicken’ clean sounds too.

In ‘Lead Guitar Tone Part 2′ I’ll mostly be discussing the non-subtle type of distorted lead sounds, but in ‘Lead Guitar Tone Part 3′ I’ll talk about the subtler kinds of distortion that clean players can make use of too.

Attack Characteristics and Compression

Along with distortion and frequency response, the attack characteristic (aka ADSR envelope) is another key factor in how we perceive a guitar’s tone. Depending on the listener/player, the attack characteristic can be a subtle after-thought, or an integral key to the person’s tone.

For guitarists, the attack characteristic is probably best described by how well a sound ‘jumps’ out of the speakers. The key to achieving a highly dynamic sound is to use very dynamic (open) pickups. Looking around online forums etc, I’ve found that most guitarists seem to prefer a highly-dynamic pickup. Open pickups will respond well to playing dynamics – stronger pick attack can drive an amp into a smooth overdrive, whilst a lighter touch can clean up well for rhythm sections. The downside to highly dynamic pickups is that, with a medium overdrive setting, the attack will likely be significantly more distorted than the sustained part of the note. Also, distortion compresses most of the dynamics out of a tone, so dynamic pickups will be of little advantage to a high-gain player. Generally speaking then, you are going to get the most benefit from pickups with a wide dynamic range, if you are using clean(er) tones.

Closely related to attack characteristics is the issue of compression. Compression is anything which serves to reduce the dynamic range of the final signal. This can include heavier strings, higher-output pickups, amplifier overdrive, distortion from pedals, heavy speaker materials, and of course dedicated compressor pedals.

The benefit of signal compression is that it raises the average level of the signal, and can also increase the perceived level of the signal as well. This means that compression makes your tone seem louder! Unfortunately, because compression is effectively reducing the dynamic range of the signal, it has the significant drawback of reducing the expressivity and musicality that can be achieved with sensitive and dynamic playing.

Controlling/manipulating the compression and attack characteristics of your final tone is something that you should do as a final touch on an already stellar tone. In a recording environment, this would mean doing it ‘in the mix’ after you’ve recorded the uncompressed guitar tone. Essentially altering the attack, or adding compression, has the potential to increase the immediacy and impact of the tone, but could also have the opposite effect of robbing the tone of its expressive potential. I’ll talk more about compression and attack in another post in this series, with some specific tips, tricks, dos and don’ts.

Summary

Controlling basic tone comes down to knowing:

  1. How much distortion – high gain or low gain
  2. What kind of distortion – symmetric or asymmetric
  3. Where in the signal chain the distortion occurs – at the pickups, the amp, the speaker or a combination of all three
  4. Which frequencies are distorted the most – distortion voicing
  5. Which frequencies are dominant
  6. Which frequencies are subdued
  7. Attack characteristics
  8. Dynamic range

P.S. Intermodulation Distortion

Before we finish up, I need to make a quick note about ‘intermodulation distortion’. This is the main distortion that we don’t want. Intermodulation distortion is the effect where signals at different frequencies combine to create signals at other, musically unrelated, frequencies.

Harmonic distortion (the good distortion) creates frequencies which we perceive as being musically related, and are pleasing to the ear (the frequencies conform to the harmonic series). However, the extra frequencies that occur in intermodulation distortion are not based on the harmonic series, and the human ear perceives it as sounding out-of-key.

The greater number of frequencies that occur simultaneously, the greater chance of noticeable intermodulation distortion. Meaning that harmonically complex signals produce stronger intermodulation distortion. Overdrive, fuzz, and ‘distortion’ pedals create their effect by increasing the harmonic content of the signal, so these pedals all increase the likelihood of objectionable intermodulation distortion. Amplifier distortion, compression, speaker distortion and virtually any kind of signal processing (such as reverb or delay) can also lead to an increase in apparent intermodulation distortion.

So, for now, the rule of thumb is to keep your distortion levels down as much as you can get away with (actually that’s good advice for other reasons too which we will soon discover). Later on, though, we’ll look at other ways of combating intermodulation distortion.

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