For my project we will explore how an electric guitar works and examine some properties of its components and sounds. We will then look at how guitar pedals and amps modify and change these sound properties.
The electric guitar is a string instrument that is designed to be electronically amplified. Like its acoustic counterpart, the most commonly found iteration of the instrument possesses six strings, a wooden body and neck, as well as the bridge, though the electric guitar lacks the hollow body and sound hole to independently amplify the vibrations of the strings. It instead boasts magnetic ‘pickups’, being magnets that pick up vibrations from the plucking or strumming of the strings to translate those oscillations into electric currents which can then be amplified or further modulated to preference. The electronic aspect enables the guitar to access and produce a variety of sounds and tones through amplifiers and effects devices that makes the instrument highly appealing and useful to a wide range of players and musical genres.
Electric guitars were invented in 1932 with the intent to be used in jazz music, but skyrocketed to popularity during the age of rock in the '60s and '70s. Electric guitars became a symbol of the era, and its iconography is still to this day associated with protest, rebellion, and counterculture. They are widely popular in many genres, as the versatility of its sound can be both striking or compliment other instruments well, which is why electric guitars tend to be the standard primary or key instrument for many bands.
Although there is some flexibility in regards to body design, the general components of an electric guitar remain somewhat standard. The particular model in the diagram is a Gibson Les Paul which is a solid-body guitar first put into mass production in 1952, at the time possessing the unique feature of using two 'humbucker' pickups rather than the more commonly used single-coil pickup.
 Headstock: Houses the tuning pegs at the head of the instrument.
 Nut: Holds the guitar strings in a set position and distance on upper part of the fretboard, thus being one of the ends of each of the vibrating open strings.
 Tuning Pegs: Knobs that can be adjusted to easily alter the individual string tension corresponding to each of the strings on the guitar in order to adjust the frequency at which the string will vibrate while playing.
 Frets: Small strips of metal that divide up the guitar neck into segments that each represent a semitone in the standard chromatic scale. Standard electric guitars have either 21 or 22 frets which give each string access to a total range of frequencies that span about an octave and a sixth. Increasingly, electric guitars with 24 frets that can access two full octaves have become more popular.
 Covered Truss Rod: A metal spine located within the neck of the guitar that keep the high tension of the steel strings from causing the wooden neck to become warped. Most modern electric guitars possess an adjustable truss rod that can be tightened or loosened to alter the tension of the neck and the distance of the strings from the surface of the fretboard.
 Fretboard Markers: Inlays that are largely decorative and not necessary for the guitar to produce sound. They usually mark the third, fifth, seventh, ninth, twelfth, fifteenth, seventeenth, and nineteenth frets.
 Neck: A solid length of wood attached to the guitar body. The flat front facing side is called the fretboard, while the back is generally a curved half cylindrical shape to ergonomically fit in the palm. The type of wood used is thought to have some impact on guitar tone as the density of the wood can affect the behavior of string vibrations.
 Cutaway: An ergonomic design choice to give players easier access to the upper frets.
 Guitar Body: A block of solid wood that can vary somewhat in shape depending on the guitar model and manufacturer. Similar to debates surrounding the impact on tone that the neck wood has, it is also thought that the type of wood used in the body can affect the overall tone.
 Magnetic Pickups: Electrical devices implemented into the guitar body that converts the vibrations of the strings into electric currents. The coil of a pickup is a length of electric wire that is wrapped around a magnet that 'picks up' the current of string vibrations. Pictured are double-coiled or 'humbucker' pickups which utilise two individual pickups to create a pattern of current flow intended to cancel out electrical interference, or to 'buck out' the 'hum'.
 Volume and Tone Knobs: Knobs that can be turned clockwise or anticlockwise to modify the signal output of the guitar.
 Bridge: Holds the guitar strings on the lower part of guitar to the body. The height of the bridge as well as the height of individual saddles can be raised or lowered to adjust the distance of the strings from the fretboard.
 Pickguard: Also called a 'scratch plate'; This is a common but optional protective guard to prevent scratches and other damage to the finish on the guitar body.
Electric guitars have a range of fundamental frequencies starting generally at 80 Hz and ranging to 1200 Hz. This ranges in pitch from around D#2/Eb2 to around D6. The tone can be altered by the tone knob, the strings, the pick selection, the amplifier, and many other properties of the guitar.
When plucked, the strings of the electric guitar will oscillate at a fundamental frequency, as well as at every following higher harmonic (2f, 3f, 4f, 5f, etc.). The pickups then "pick up" the oscillations via magnets physically moving due to the oscillation of the strings upon them. These magnets then transmit those oscillations to magnetic coils within the pickups, which translate the physical oscillations into electric currents. These electric currents then run from the pickups through the input jack and attached cable to an amplifier, which produce the sound. This is in contrast with an acoustic guitar, where the strings cause the bridge to oscillate and the bridge causes the body to oscillate in turn.
Volume and tone are controlled by knobs on the body of the guitar. When turned, the volume knob amplifies the waves of the electric current running through the guitar, and the tone knob, when turned, specifically suppresses the higher frequencies of the guitar to create a darker tone, in a sense like how the vocal tract filters formant frequencies to produce a final sound.
There are a few types of amplifiers, but only two that we will be discussing here: tube amps and solid state amps. Both have the same function: to amplify the amplitude of oscillations produced by electric guitars in order to be able to actually hear them. When electrical currents hit the amp, they are multiplied using either vacuum tubes (in tube amps) or an electronic transistor (in solid state amps). Then they project the sound the same way a speaker would, by using the electric current to oscillate a magnet, which in turn oscillates a flat surface or membrane to "play" the sound.
Tube amps were developed first, before transistors were invented. Both are still used today, but tube amps are essentially the analog equivalent of solid state amps. In tube amplifiers, electrons flow through the tubes. Too much of this can overwhelm the vacuum tubes, which may lead to harmonic distortion. Solid state amps don't have this problem, but often the distortion of the vacuum tubes is desired for a specific sort of tone and as such there are certain pedals and effects that solid state amps have been programmed with in order to be able to controllably replicate this distortion.
An effects pedal or guitar pedal is a physical device that modulates and alters an audio signal. These are manually operated by the player as they play the electric guitar that is connected to the device, either by switching the pedal on before beginning to play or by actively toggling the pedal on and off with their foot. The commonly used term "stompbox" refers to such pedals that can be stomp-toggled on.
An effects pedal cannot produce or emit sound on its own and, besides the input from the electric guitar, also needs to be connected to an amplifier to amplify any audio output. The most popular effects are generally some combination of overdrive, distortion, and fuzz pedals which are most recognisable as producing a standard quintessential 'rock sound', though any number of effects can be used either separately or together to create unique noises.
These effects greatly expand the range, variety, and creativity of the electric guitar sound, with certain effects even functioning as the key feature of certain musical genres and movements. For example, "Shoegaze" is a sub-genre of rock music originating from the late '80s and '90s where the stacking of multiple effects pedals together was crucial for creating the loud, layered, full-bodied, and almost surreal sound. It takes its name from the performance demeanour guitarists had to adopt while playing as they stared downwards at the floor to toggle their various effects pedals on and off.
When an electric guitar is run through an effects pedal, the string vibrations are converted into electric currents by the pickups, which are then sent through wires to the guitar pedal which electronically modifies the time varying electrical current according to the type of pedal used and its specified presets. This modified signal will then be sent to the amplifier, which converts it back into sound waves. Effects can be broadly classified in two categories, being either signal reshaping or signal augmentation .
Effects under this classification primarily involve an alteration of the signal that affects the overall shape of the sound wave. This includes effects such as overdrive, distortion, compression, ring modulation, and pitch shifting, all of which tend change the nature of the original sound entirely.
Effects under this classification primarily involve the addition or splitting of signals to provide extra separate sound waves in addition to the original. This includes effects such as flanging, phasing, chorus, delay, echo, and reverb, in which the primary impact is the inclusion of additional sounds, though some mild alteration of the signal may also occur.
Impact of Effects Pedal on the Sound of Electric Guitar
The basic demonstration below examines the differences between the base unmodulated 'clean tone' of the open D string on a 'Fender Telecaster' electric guitar and the modified tone of the same open D string after the guitar is run through an 'EHx Green Russian Big Muff Pi' fuzz pedal. When the original signal from the vibration of the guitar string reaches the pedal, the signal gets distorted through an electrical generation of additional harmonics, the number of which increases the higher the distortion or gain knobs are increased. The pedal essentially forces the peaks and valleys of the sound waves to clip and become compressed, distorting the waves into ones that are more angular or jagged in shape.
In the earlier decades of electronic music's ascent to mainstream, distortion and fuzz effects could easily be achieved with vacuum tube-style amplifiers alone, since levels beyond the specified maximum amplification would clip the peaks of the waveforms by default, thus producing a staticky and 'dirty' sound. Fuzz pedals like the model utilised in this demonstration are more commonly used in the twenty-first century in which a square wave generator introduces square frequency waves that add to or replace the initial signal. This particular model also adds several additional harmonic overtimes to artificially round out the sound to produce a warmer tone, while raising the gain knob simulate the more traditional kind of tube-style distortion.
In the spectrum graph of the recorded clean tone, the harmonics are much more condensed around the fundamental frequency (In this case being the note D3, at 147Hz), with the subsequent higher harmonics decreasing in amplitude. The sound wave of the clean tone is a relatively smooth sinusoidal wave comprised of smaller spiked curves which is likely the electrical feedback and buzz of the amplifier being picked up in the recording.
In the spectrum graph of the recorded modulate tone with the fuzz effect, the mid and upper frequencies have been boosted significantly, increasing the range of harmonics following the fundamental frequency at higher amplitudes. While the fundamental frequency of the D3 note is still discernible, the prominent presence of additional harmonics muddy the overall sound. The sound wave of the fuzz tone is drastically different in shape from the clean tone, having much sharper, angular, and asymmetrical peaks and valleys. Although it is somewhat obscured by the feedback and buzz from recording the sound of the amplifier, an analysis of this signal through an oscilloscope would reveal the squared angular nature of the sound waves characteristic of fuzzboxes of the kind being used.
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