Electric Guitar Sounds

The electric guitar is a musical instrument based on the traditional acoustic guitar but designed for sound generation involving electrical means. In contrast to a classical concert guitar, which makes the string vibrations audible via (mechanical) excitation of a hollow body structure, the electric guitar has an electric pickup to sense the string vibrations and feed the resulting signal to a electronic sound processing and amplification devices, and eventually to a loudspeaker (or headphones). ^[Lemme]

Over the decades, electric guitars from certain brands have become established in various music genres; sometimes even individual models have started to play important roles. There are endless numbers of brands, types, and models (and their variations) on the market. This raises the question: How different do the guitars actually sound? And which factors – from the player and the guitar itself via associated gear to the listening environment - do in fact influence the sound?

In order to clarify these questions at least to an extent, tests have been carried out with professional guitarists and a wide selection of guitars. The tests examined how the guitars themselves differ from each other in terms of sound, what influence the playing style and the electronics on the guitar have, and how the instrument cables can affect the sound. In addition, the influence of the microphones used to record the amplifier was also investigated, as well as of the position of these microphones in front of the loudspeaker cabinet.

The procedure and results are documented in the subpages.

Like in the acoustic guitar, the elements of the electric guitar primarily consist of a body and a fretted neck (both usually made of wood) over which in most cases 6 strings are stretched - although there are also 4-string, 7-string, 9-string and 12-string instruments. Other numbers of strings are very rare. Multi-neck-instruments are also occasionally in use. To make the guitar "electric", one or more pickups sensing the string vibrations are installed, and also associated controls. A device often seen on electric guitars is a so-called vibrato bar. This is a lever which enables the player to change the tension (and thus the pitch) of the strings in mid-playing. ^[Lemme]

Construction

Most electric guitars have a solid wooden body, but partly-hollow (i.e. semi-solid) and fully-hollow bodies are also common. Due to the fact that an electric amplification is the means of make the sound audible, the shape of the body is not as relevant, and especially solid-body guitars may be given all kinds of shapes and sizes Ergonomics and cosmetic appeal are the deciding factors here.  High-quality woods are often used to build electric guitars, even though the acoustic properties of the wood are of little relevance to the sound of an electric guitar for semi-solid and hollow bodies, and even almost totally irrelevant for solid bodies. ^[Zollner]

Types
When it comes to solid-body guitars, today's guitar market is based to a large extent on three electric guitar designs: the Telecaster and the Stratocaster (built originally by the Fender company), and the Les Paul (built originally by the Gibson company). These three types have spawned a myriad of successors, derivatives, signature editions, modifications, and replicas from both their original manufacturers, and from a large number of other manufacturers.

The Fender Telecaster was designed by Leo Fender and went into production by 1950 ^[Bacon]. It was the first commercially successful solid-body electric guitar. As a competing product, Gibson developed the Les Paul guitar and marketed it in 1952 ^[Carter]. Fender's highly successful Stratocaster was released in 1954 ^[Bacon].

Initially, electric guitars were of a basically conventional acoustic-guitar design (with a hollow body) and fitted with electromagnetic pickups. The Gibson company was the first to market an electric guitar which had any commercial impact; this was in 1935 ^[Carter]. The construction of these early electric guitars with hollow bodies was soon modified to better accommodate the needs to the players, and among other aspects led to so-called thin-line instruments (with a shallow hollow body), and eventually to the semi-solid guitars. The latter have only a partially hollow body and sound close or even identical to solid-body instruments ^[Zollner]. Some famous proponents of the fully hollow electric guitar are the models ES-175, ES-5, and Super 400 manufactured by the Gibson company. Gibson also manufactured the ES-330 thin-line guitar, as well as the ES-335, ES-345, and ES-355 as the most famous semi-solid instruments ^[Duchossoir].

Most other manufacturers generate variations of the instruments mentioned above.   

Pickups
Electric guitars mostly feature electromagnetic pickups mounted underneath the strings. There are number of different design approaches but the two most often found are the so-called single-coil pickup, and the humbucking pickup.

A single-coil pickup consists of a coil wound around one or several permanent magnets, or around one or several iron pole pieces with a magnet fixed on the underside of the coil. As the string vibrates above the pickup, it modulates the magnetic field and thus induces in the coil an alternating voltage with the frequency of the string vibration. The single-coil pickup is more typically found in Fender guitars, although Gibson does also produce such pickups, e.g. the famous P-90 design.^[Zollner]

A humbucker (also hum-compensation coil) pickup basically consists of two coils wound in opposite directions, and subjected to opposite directions of the magnetic field (due to arranging the magnet in a conducive manner). Due to the opposite directions of both the winding and the magnetic field, the voltages induced by the string in the two coils add up in-phase while any voltages induced from external sources into the coils ideally cancel each other out. This structure considerably reduces the susceptibility to hum interference. The Gibson company is famous for the introduction of the Humbucking pickup in 1957 (e.g. in the Les Paul guitar) although other manufacturers started producing similar pickup designs around the same time also.^[Zollner]

The voltage generated by such pickups is in the order of between 50 mV for weak pickups and up to 1 V for very strong pickups. 

Depending on position of the pickup between the end of the neck and the bridge, the sound will be different since harmonics of the string vibration are represented to different degrees along the variation of the position. 

As an example, the Fender Stratocaster (see the picture on the right), has three single coil pickups. The positions of these pickups are designated "neck", "middle", and "bridge". The neck pickup is positioned close to the neck, while the bridge pickup is mounted close to the bridge assembly.

Switches and Knobs
Electric guitars usually have switches and controls mounted to change the sound or volume of the instrument.

For example, the pickup selector switch allows for selecting individual pickups or combinations of pickups. With the Fender Stratocaster, a lever-switch allows for five possible configurations of the three pickups:

In the intermediate positions, the two involved pickups interact and may also have the hum-supression effect of a humbucker.

For a guitar with two pickups (often in humbucking configuration), 3 configurations are typically possible:

The sound achieved via the different pickup positions is of a more trebly and sharper character for the pickup at the bridge position, and fuller and warmer for the pickup at the neck position.

When two pickups are selected in combination, they are usually wired in a parallel configuration although there are some electric guitars fitted with the option to connect the pickups in series which yields a darker and fuller sound.^[Lemme]

Usually, there are one or more volume controls (often one for each pickup) and one or more "tone" controls (again often one for each pickup). The latter usually have a treble-cut (low-pass) effect, and/or they dampen or modify the electrical resonance of the pickup in the upper frequency range (see influence of instrument cables). However, bass-cut (high-pass) filter configurations are found in a few cases, as well.  ^[Lemme]

Amplifiers
The motivation for developing electric guitars was to amplify the electrical signals so that the guitar is loud enough in a band context. This amplification is done with the guitar amplifier (short form "amp") and a loudspeaker connected to it. Amp and speaker may be housed in combination in one box; this design is called "combo" amplifier. Interestingly, amplifiers with tubes are still preferred to this day by many guitarists.

The selection and combination options for amplifiers on the market are endless. The products from Fender and Marshall are particularly well known, but other brands are also preferred depending on the genre, the taste, and the requirements of the player ^[Fliegler]. In the age of digital signal processors (DSP), all amplifier sounds can be emulated very realistically. 

Effects-devices (sound processors) cover a very broad spectrum of sound shaping; they are often connected in the signal path between the guitar output and amplifier input. In many cases, these devices have the form of small boxes that are placed on the floor close to the guitar player. They are then activated via foot switches and interconnected via so-called patch cables (short instrument cables).

In recording sessions with professional guitarists, several sound recordings were made under controlled conditions.

In a guitar comparison, the influence of each guitar on the sound was recorded. All other parameters were kept as constant as possible. By changing the pickup selector switch position, at least three recordings were made for each guitar and genre.

Playing style has a very important influence on the sound of an electric guitar but is extremely difficult to measure technically. Therefore, acoustic comparisons based on recordings are crucial. The influence of playing style is examined in this subsection.

In the pick comparison, the tonal impact of different picks (or plectrums) was analyzed. Various shapes and thicknesses of picks were considered.

Instrument cables are used for signal transmission between the guitar and the amplifier. The length of this cable usually affects the sound heard at the speaker output. This test relates to the influence of instrument cables.

Guitar loudspeakers have a significant influence on the sound due to their irregular and often characteristic frequency response. Instead of taking signals directly from the amplifier output for recording (as is quite common with electric basses), microphones positioned in front of the loudspeaker membrane are used. The choice of microphones is looked into in this microphone comparison (electric guitar).

The positioning of the microphone in front of the speaker has also a significant tonal influence. The microphone comparison at the guitar amplifier illustrates this.

Additionally, there are many other sound-forming elements that were not investigated in the above recording sessions. Among these are, for example: