Science Fair Project Encyclopedia
Guitars have a body (hollow in acoustic guitars, solid in most electric guitars) and a neck. Typically, a headstock extends from the neck for tuning.
Guitars are used in a wide variety of musical styles. They are made and repaired by luthiers.
Instruments like the guitar have been popular for at least 5,000 years; murals in Egypt show women playing instruments like the guitar from the time of the Pharaohs, but the name guitar appears first in Spain in the 13th century. It probably originated from a Persian word Gui-Tar meaning a half sphere and strings. It might, as well, be a derivation of the Arabic word qitara, the name of an instrument that was brought into Spain by the Moors after the 10th century. (See related article). It also may have been derived from the word sitar, a similar centuries-old musical instrument and musical symbol of Hindu goddess Saraswati.
The Spanish vihuela appears to be an intermediate form, with lute-style tuning and a small guitar-style body, but it is not clear whether this represents a transitional form or simply a design that combined features from the two families of instruments.
The electric guitar was invented by Adolf Rickenbacker, with the help of George Beauchamp and Paul Berth, in 1931. Rickenbacker was the inventor of the horseshoe-magnet pickup. However, it was Danelectro that first produced electric guitars for the wider public. Danelectro also pioneered Tube Amp technology.
Parts of the guitar
The headstock is located at the end of the guitar neck. The headstock usually consists of machine heads (used for tuning), a "nut" (marking the end of the playable section of the strings) and a logo identifying the maker or model of the guitar. Some guitars lack headstocks, for decreased size, decreased weight, or for aesthetic reasons. (1)(2)
Machine heads or tuners or tuning keysMachine heads are designed to adjust the tension of the strings, raising or lowering their pitch to tune the instrument. While machine heads are typically screwed into the headstock and designed with gears to allow finer tuning, some simpler designs simply involve wooden pegs held in place by friction.
There are three types of machine head on modern steel-strung guitars:
- Open back (where the gear itself is exposed);
- Closed back (where the gear is covered and the occasional lubrication of the gear can be done through a small hole in the cover);
- Sealed (closed back, but permanently and completely sealed and lubricated, eliminating any maintenance).
These may be arranged on the headstock in two rows of three, as on the Gibson Les Paul and the majority of acoustic guitars, or six in line, as on the Fender Stratocaster. Another arrangement, notably less popular, is one row of four on the playing side and one row of two on the opposite side. Music Man guitars feature this type of setup.
Nearly all modern nylon-strung (or classical) guitars use open geared machine heads.
NutThe nut is a small strip of ivory, bone, plastic, graphite, or other medium-hard material that braces the strings at the joint where the headstock meets the fretboard. It is grooved to hold the strings in place, and it is one of the endpoints of the strings' tension (the other being the saddle of the bridge). The nut also helps determine the action -- the distance between the fretboard and the strings.
Alternatively called the fingerboard, the fretboard is a long plank of wood embedded with metal frets that comprises the top of the neck. It is flat on classical guitars and slightly curved crosswise on acoustic and electric guitars. Pinching a string against the fretboard effectively shortens the vibrating length of the string, producing a higher tone (a string, unfingered, will vibrate from the saddle to the nut; once fingered, it will vibrate only along the distance between the saddle and the fret directly before the finger). Fretboards are most commonly made of rosewood, ebony, and maple.
FretsFrets are metal strips (usually nickel alloy) embedded along the fretboard. When strings are pressed down behind them, frets shorten the strings' vibrating lengths to produce different pitches. For more on fret spacing, see the Strings and Tuning section below. Frets are usually the first permanent part to wear out on a heavily played guitar. They can be re-shaped to a certain extent and can be replaced as needed. Frets also indicate fractions of the length of a string (the string midpoint is at the 12th fret; one-third the length of the string reaches from the nut to the 7th fret, the 7th fret to the 19th, and the 19th to the saddle; one-fourth reaches from nut to fifth to twelfth to twenty-fourth to saddle). This feature is important in playing harmonics. Frets are available in several different gauges, depending on the type of guitar and the player's style.
Truss rodThe truss rod is an adjustable metal rod that runs along the inside of the neck, adjusted by an allen-key bolt usually located either at the headstock (under a cover) or just inside the body of the guitar, underneath the fretboard (accessible through the sound hole). The immense amount of tension the strings place on the neck can sometimes bend it forward, and changes in humidity can warp the wood slightly. The truss rod allows the neck to be adjusted to accommodate these changes -- tightening it will curve the neck back and loosening it will return it forward. Some truss rod systems, called "double action" truss systems, will tighten both ways, allowing the neck to be pushed both forward and backward (most truss rods can only be loosened so much, beyond which the bolt will just come loose and the neck will no longer be pulled backward).
InlaysInlays are dots, diamond shapes, lightning bolts, or letters and numbers that are set into the fretboard of the guitar, between frets. They are often done in plastic on guitars of recent vintage, but many older, and newer, high-end instruments have inlays made of mother of pearl, abalone, ivory, or any number of exotic materials. On some low-end guitars, they're just painted. There are single inlays on the 3rd, 5th, 7th, 9th, 15th, 17th, 19th and 21st frets, and double inlays on the 12th, sometimes 7th, and (if present) 24th frets.
NeckA guitar's frets, fretboard, tuners, headstock, and truss rod, all attached to a long wooden extension, collectively comprise its neck. The wood used to make the fretboard will usually differ from the wood in the rest of the neck. The bending stress on the neck is considerable, particularly when heavier gauge strings are used (see Strings and tuning), and the ability of the neck to resist bending (see Truss rod) is important to the guitar's ability to hold a constant pitch during tuning or when strings are fretted. The rigidity of the neck with respect to the body of the guitar is one determinant of a good instrument versus a poor one. Conversely, the ability to change the pitch of the note slightly by deliberately bending the neck forcibly with the fretting arm is a technique sometimes used, particularly in the blues genre and those derived from it, such as rock and roll. The shape of the neck can also vary, from a gentle "C" curve to a more pronounced "V" curve.
Neck jointThis is the point at which the neck is either bolted or glued to the body of the guitar. Almost all acoustic guitars, with the primary exception of Taylors, have glued (or set) necks, while electric guitars are constructed using both types. Set necks usually feature dovetail joints, which offer stability and sustain. Bolt-on necks, though they are often associated with cheaper instruments, do offer greater flexibility in the guitar's set-up.
Some very high-end instruments may not have a neck joint at all, having the neck and sides built as one piece and the body built around it.
Body (acoustic guitar)The body of the instrument is a major determinate of the overall sound for acoustic guitars. The guitar top, or soundboard, is a finely crafted and engineered element often made of spruce, cedar or mahogany. This thin (often 2 or 3 mm. thick) piece of wood, strengthened by different types of internal bracing, is considered to be the most prominent factor in determining the sound quality of a guitar. The majority of the sound is caused by vibration of the guitar top as the energy of the vibrating strings is transferred to it. Different patterns of wood bracing have been used through the years by luthiers; to not only strengthen the top against collapsing under the tremendous stress exerted by the tensioned strings (Torres, Hauser, Ramirez, Fleta being among the most influential designers of their time), but also to affect the resonation of the top. The back and sides are made out of a variety of woods such as mahogany, Indian rosewood and highly regarded Brazilian rosewood (Dalbergia nigra). Each one is chosen for their aesthetic effect and structural strength, and can also play a significant role in determining the instrument's timbre. These are also strengthened with internal bracing, decorated with inlays and purfling, and subjected to a lot of abuse.
Body (electric guitar)Most electric guitar bodies are made of wood. This wood is rarely one solid piece, as laminating hardwoods in the proper way can produce a body of exceptional strength and superior tone. The most common woods used for electric guitar body construction include maple, basswood, ash, poplar, alder, and mahogany. Many bodies will consist of good sounding but inexpensive woods, like ash, with a "top", or thin layer of another, more attractive wood (such as maple with a natural "flame" pattern) glued to the top of the basic wood. Guitars constructed like this are often called "flame tops". The body is usually carved or routed to accept the other elements, such as the bridge, pickup, neck, and other electronic components.
Resonating chamberUsually on acoustic guitars, the resonating chamber or sound hole allows the acoustic guitar to be played without amplification. It is normally a round hole in the top of the guitar, though some may have different shapes or multiple holes. This allows the vibrations from the back and sides of the guitar to be pushed forward toward the listener.
PickupsThe electric guitar is usually not very loud when played without an amplifier. Pickups allow the vibrations of the string to be amplified. Some acoustic guitars also have microphones or pickups built into them for stage work. Pickups work on a similar principle to a generator in that the vibration of the strings causes a small current to be created in the coils surrounding the magnets. This signal is later amplified by an amplifier. However, a new type of pickup, called a Q-Tuner pickup, has been developed that measures the magnetic flux density of multiple magnets located in the pickup. This produces a better tone and picks up harmonic frequencies better that standard pickups, but these cost more and are more difficult to wire.
ElectronicsThese components and the wires that connect them allow the player to control some aspects of the sound like volume or tone. These at their simplest consist of passive components such as potentiometers and capacitors, but may also include specialized integrated circuits or other active components requiring batteries for power, for preamplification and signal processing, or even for assistance in tuning. In many cases the electronics have some sort of magnetic shielding to prevent pickup of external interference and noise.
This is the decorative edge found around the body of an acoustic guitar. Its purpose is not merely decorative, however. Because of the construction methods, the edges of the body are typically the weakest point of the acoustic guitar. There is not much wood there, as the sides have to be thin to allow for bending, and the top and back have to be thin to allow the string vibrations to resonate. Trying to connect two thin pieces of wood at a 90 degree angle is an engineering challenge. So to help, the purfling is used. The corners are overbuilt, using a triangular piece of scored wood (called a kerfed lining) on the interior of the instrument to allow it to follow the contours, and is glued in place. During final construction, a small section of the outside corners is carved or routed out and then filled in with the purfling material. Today, it is almost exclusively high quality plastic. Once the purfling is glued in place, it is an integral part of the guitar, and contributes greatly to its durability, since plastic tends not to split as wood does when impacted.
BridgeThe main purpose of the bridge on an acoustic guitar is transfer the vibration from the strings to the soundboard, which vibrates the air inside of the guitar, thereby amplifying the sound produced by the strings.
On both electric and acoustic guitars, the bridge holds the strings in place. From there, the variations are astounding. There may be some mechanism for raising or lowering the bridge to adjust the distance between the strings and the fretboard (action), and/or fine-tuning the intonation of the instrument. Some are springloaded with a "whammy bar", a removable arm which allows the player to modulate the pitch by pulling the strings completely slack, then releasing the bar to restore the original tension. The whammy bar is sometimes incorrectly referred to as a "tremolo bar"--unlike the change in pitch that the whammy bar produces, a tremolo is a quick oscillation of the volume. Some bridges allow for alternate tunings at the touch of a button.
PickguardThis is usually a piece of plastic or other laminated material that protects the finish of the top of the guitar. In some electric guitars, the pickups and most of the electronics are mounted on the pickguard. On acoustic guitars and many electric guitars, the pickguard is mounted directly to the guitar top, while on guitars with carved tops (e.g. the Gibson Les Paul), the pickguard is elevated.
Strings and tuning
Guitars have frets on the fingerboard to fix the positions of notes and scales, which gives them equal temperament. Consequently, the ratio of the widths of two consecutive frets is , whose numeric value is about 1.059463. The twelfth fret divides the string in two exact halves and the 24th fret (if present) divides the string in half yet again. Every twelve frets represents one octave.
Guitars usually have six strings, although there are variations on this, the most common being a twelve-string guitar, the seven string guitar, the ukulele, which has four strings, and the bass guitar, which usually has four strings but also exists in five, six, eight, and twelve-string versions. There are also more exotic models involving multiple necks and pickups. The vihuela, a guitar variation which emerged in 16th century Spain, has six double strings made of gut.
The weight of a string is determined by its diameter and is normally measured in thousandths of an inch. The larger the diameter the heavier the string is (with thinner strings being lighter). Heavier strings require more tension for the same pitch and are consequently harder to hold on to the fretboard. Heavier strings will also produce a louder note and for this reason steel-strung acoustic guitars will normally be strung heavier than electric guitars.
A variety of different tunings are used. The most common by far, known as "standard tuning", is as follows:
- sixth (lowest) string: E (a minor thirteenth below middle C—82.4Hz)
- fifth string: A (a minor tenth below middle C—110Hz)
- fourth string: d (a minor seventh below middle C—146.8Hz)
- third string: g (a perfect fourth below middle C—196.0Hz)
- second string: b (a minor second below middle C—246.92Hz)
- first (highest) string: e' (a major third above middle C—329.6Hz)
Standard tuning has evolved to provide a good compromise of both simple fingering for many chords, and the ability to play common scales with minimal left hand movement. Additionally, the separation of all adjacent string pairs except one (G-B) by the same interval, a perfect fourth (equivalent to 5 frets' distance), yields a symmetry and intelligibility to fingering patterns in this tuning. The major third (four frets' distance) between the g and b strings, though undermining this clarity, facilitates the playing of many chords and scales as mentioned above and, more generally, provides some diversity in fingering possibilities; many figures which are difficult to play on strings tuned a fourth apart are easy to play on strings tuned a third apart and vice versa.
Some common alternate tunings:
- E-A-d-f#-b-e which provides the same intervals as for a renaissance lute and so you can play with your guitar directly from tablature.
- D-G-d-g-b-d, open g tuning commonly used for blues or slide guitar
- D-A-d-f#-a-d, open d tuning commonly used in blues and folk
- E-B-e-g#-b-e, open e tuning one step up from open D
- D-A-d-g-b-e', the drop d tuning frequently used in folk music, and by metal and alternative-rock bands
- E-a-d-g-c'-f', all fourths tuning removes from the standard tuning the irregularity of the interval of a third between the fourth and fifth strings. The tuning is in fourths like that of the lowest four strings in standard tuning. With regular tunings like this, chords can simply be moved down or across the fretboard, dramatically reducing the number of different finger positions that need to be memorized. The disadvantage of all fourths is that not all major and minor chords can be played with all six strings at once.
- C-G-d-a'-e'-b', all fifths tuning is in fifths like that of a mandolin or a violin and has a remarkably wide range.
- C-G-d-a-e-g, the new standard tuning devised by Robert Fripp of King Crimson, used by most Guitar Craft students around the world. The tuning is like all fifths except the most treble string is dropped down from b' to g.
- D-A-d-g-a-d' frequently used in Celtic music, and by artists such as Pierre Bensusan .
Note that a standard guitar sounds one octave below pitch as written in standard notation. Therefore, the pitch of the top string in standard tuning actually sounds as a major third above middle C, despite being written as a major tenth above middle C.
There are also tenor guitars , baritone guitars tuned ADGCEA (or GDGCDG, GDGCEA, GCGCEG, etc.) a fifth lower than a normal guitar, treble guitars tuned a fourth higher than a standard (prime) guitar, and contrabass guitars, which are tuned one octave lower than prime guitars.
Acoustic and electric guitar
Broadly speaking, guitars can be divided into 2 categories:
- Acoustic guitars: Unlike the electric guitar, the traditional guitar is not dependent on any external device for amplification. The shape and resonance of the guitar itself creates acoustic amplification. However, the unamplified guitar is not a loud instrument, that is, it cannot compete with other instruments commonly found in bands and orchestras, in terms of sheer audible volume. Many acoustic guitars are available today with built-in electronics to enable amplification. There are several subcategories within the acoustic guitar group: classical and flamenco guitars, both of which use nylon and composite strings, and steel string guitars, which includes the flat top, or "folk" guitar, the closely related twelve string guitar, and the arch top guitar. A recent arrival in the acoustic guitar group is the acoustic bass guitar, similar in tuning to the electric bass.
- Renaissance and Baroque guitars: These are the gracile ancestors of the modern classical guitar. They are substantially smaller and more delicate than the classical guitar, and generate a much quieter sound. The strings are paired in courses as in a modern 12 string guitar, but they only have four or five courses of strings rather than six. They were more often used as rhythm instruments in ensembles than as solo instruments, and can often be seen in that role in early music performances. (Gaspar Sanz ' Instrucción de Música sobre la Guitarra Española of 1674 constitutes the majority of the surviving solo corpus for the era.) Renaissance and Baroque guitars are easily distinguished because the Renaissance guitar is very plain and the Baroque guitar is very ornate, with inlays all over the neck and body, and a paper-cutout inverted "wedding cake" inside the hole.
- Classical guitars: These are typically strung with nylon or gut, and amplification is provided by the resonant hollow body, and the vibration of the thin, pliant top. In all acoustic guitars, the strings, though vibrating with sufficient energy to produce a strong sound, can not do so by themselves because they are too small and thin: air merely slips around them rather than being projected outward. The joining of the strings to a large membrane, the top, which they pull back and forth where they connect to it at the bridge, creates an effective air-moving system because the top is large enough that the air can not readily side step its motion. Sound only travels at 330 meters per second -- somewhat quickly, perhaps -- but if we recall that a guitar string typically switches from backward motion to forward motion every 1/600th of a second, we see that the air only has a chance to go about 1/2 meter, and the approximately 1/2 meter dimensions of a guitar top are enough to thwart its attempted evasive rush.
These guitars are normally played in a seated position and used to play classical music. Flamenco guitars are almost equal in construction, have a sharper sound, and are used in flamenco. In Mexico, the popular mariachi band includes a range of guitars, from the tiny requinto to the guitarron, a guitar larger than a cello, which is tuned in the bass register. The father of the modern classical guitar was Antonio Torres Jurado.
- Flat top guitars : Similar to the classical guitar, however the body size is usually significantly larger than a classical guitar and it has a narrower, reinforced neck and stronger structural design, to sustain the extra tension of steel strings which produce a louder and brighter tone. The acoustic guitar is a staple in folk, Old-time music and blues music.
- Resonator, resophonic or dobro guitars: Similar to the flat top guitar in appearance, but with sound produced by a metal resonator mounted in the middle of the top rather than an open sound hole, so that the physical principle of the guitar is actually more similar to the banjo. The purpose of the resonator is to amplify the sound of the guitar; this purpose has been largely superseded by electrical amplification, but the resonator is still played by those desiring its distinctive sound. This type of guitar is more commonly played face up, on the lap of the seated player, and often with a metal or glass slide.
- 12 string guitars usually have steel strings and are widely used in folk music and rock and roll. Rather than having only six strings, the 12-string guitar has pairs, like a mandolin. Each pair of strings is tuned either in unison (the two highest) or an octave apart (the others). They are made both in acoustic and electric forms.
- Archtop guitars are steel string, instruments which feature a violin-inspired f-hole design in which the top (and often the back) of the instrument are carved in a curved rather than a flat shape. Lloyd Loar of the Gibson company invented this variation of guitar after designing a style of mandolin of the same type. The typical Archtop is a hollow body guitar whose form is much like that of a mandolin or violin family instrument and may be acoustic or electric. Some solid body electric guitars are also considered archtop guitars although usually 'Archtop guitar' refers to the hollow body form. Archtop guitars were immediately adopted upon their release by both jazz and country musicians and have remained particularly popular in jazz music, usually using thicker strings (higher guaged round wound and flat wound) than acoustic guitars. Archtops are often louder than a typical dreadnought acoustic guitar. The electric hollow body archtop guitar has a distinct sound among electric guitars and is consequently appropriate for many styles of rock and roll. Many electric archtop guitars intended for use in rock and roll even have a Tremolo Arm.
- Acoustic bass guitars also have steel strings, and match the tuning of the electric bass, which is likewise similar to the traditional double bass viol, the "big bass", a staple of string orchestras and bluegrass bands alike.
- Electric guitars: Electric guitars can have solid, semi-hollow or hollow bodies, and produce little or very low sound without amplification. Electromagnetic pickups (single and double coil) convert the vibration of the steel strings into electric signals which are fed to an amplifier through a cable or radio device. The sound is frequently modified by other electronic devices or natural distortion of valves (vacuum tubes) in the amplifier. The electric guitar is used extensively in blues and rock and roll, and was commercialized by Gibson together with Les Paul and independently by Leo Fender. The lower fretboard action (the height of the strings from the fingerboard) and its electrical amplification lend the electric guitar to some techniques which are harder (or impossible) to execute on acoustic guitars. These techniques include tapping, extensive use of legato through pull-offs and hammer-ons (a.k.a. slurs in the traditional Classical genre), pinch harmonics, volume swells and use of a Tremolo arm or effects pedals.
The electric bass is similar in tuning to the traditional double bass viol. Hybrids of acoustic and electric guitars are also common. There are also more exotic varieties, such as double-necked guitars, all manner of alternate string arrangements, fretless fingerboards (almost always reserved for bass guitars, meant to emulate the sound of a stand-up bass), and such.
The guitar has come to be called many different colloquial names over time such as: axe, shredder, teeth flosser, and box-o-strings.
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- Free Guitar Lessons Beginner guitar lessons for free -- including tablature to the Beatles, Led Zeppelin, and other classic rock songs, chords, and more...
- Guitar Tabs has some cool guitar tabs available for free use, great resource.
- Photos of replica Renaissance and Baroque guitars can be found among the lutes at Wayne Cripps' lute pages.
- Fretland Acoustic guitar products, reviews and tips.
- The history of guitar-like instruments from 1900 B.C. through modern times is summarized at Classical Guitar Illustrated History
- Granary-Guitars - A collection of fine classical guitars in Hertfordshire, United Kingdom, which is occasionally open for viewing and playing.
- Classic Cat has on its Classical Guitar Mp3 Page an overview of some 100 free guitar mp3s on the internet.
- Guitar Noise Great articles on theory and practise of Guitar.
- Guitar Tabs Axetopia has a good resource list and search.
- More Guitar Tabs Over 95,000 guitar tabs online.
- Guitar Directory is a nice searchable web directory with thousands of guitar-oriented sites and site reviews.
- Dansms features guitar theory articles, including modes, scales, and keys.
- Guitar Tuning Tips has information on basic tuning, along with alternative guitar tunings.
- Tabble.com: Guitar Tabs Contains guitar tablature from many artists and bands. Sorted alphabetically by band. Search included.
- A Guide to Jazz Guitar is all about jazz guitar: tabs, lessons, mp3, transcriptions.
- GuitarGearHeads is a free resource for lessons and professional gear reviews.
- ZWorkbench has some cool guitar software that works on your cell phone. They have a metronome, pitch pipe, and chord reference.
- An example of one of many online sellers of guitars, amplifiers etc. Guitar Catalog Online
- Guitar Wiki — a wiki-based guitar resource
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