A
bridge is a device for supporting the
stringsA string is the vibrating element that is the source of vibration in string instruments, such as the guitar, harp, piano, and members of the violin family. They are lengths of a flexible material kept under tension so that they may freely vibrate...
on a stringed instrument and transmitting the
vibrationVibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road.Vibration is occasionally "desirable"...
of those strings to some other structural component of the instrument in order to transfer the
soundSound is a travelling wave which is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.- Perception of sound...
to the surrounding air.
Most stringed instruments produce their sound through the application of
energyIn physics, energy is a scalar physical quantity that describes the amount of work that can be performed by a force, an attribute of objects and systems that is subject to a conservation law...
to the strings, which sets them into vibratory motion. The strings alone, however, produce only a faint sound because they
displaceParticle displacement or particle amplitude is a measurement of distance of the movement of a particle in a medium as it transmits a wave. In most cases this is a longitudinal wave of pressure , but it can also be a transverse wave, such as the vibration of a taut string...
only a small volume of air as they vibrate.
A
bridge is a device for supporting the
stringsA string is the vibrating element that is the source of vibration in string instruments, such as the guitar, harp, piano, and members of the violin family. They are lengths of a flexible material kept under tension so that they may freely vibrate...
on a stringed instrument and transmitting the
vibrationVibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road.Vibration is occasionally "desirable"...
of those strings to some other structural component of the instrument in order to transfer the
soundSound is a travelling wave which is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.- Perception of sound...
to the surrounding air.
Explanation
Most stringed instruments produce their sound through the application of
energyIn physics, energy is a scalar physical quantity that describes the amount of work that can be performed by a force, an attribute of objects and systems that is subject to a conservation law...
to the strings, which sets them into vibratory motion. The strings alone, however, produce only a faint sound because they
displaceParticle displacement or particle amplitude is a measurement of distance of the movement of a particle in a medium as it transmits a wave. In most cases this is a longitudinal wave of pressure , but it can also be a transverse wave, such as the vibration of a taut string...
only a small volume of air as they vibrate. Consequently, the sound of the strings alone requires
impedance matchingImpedance matching is the electronics design practice of setting the input impedance of an electrical load equal to the fixed output impedance of the signal source to which it is ultimately connected, usually in order to maximize the power transfer and minimize reflections from the load...
to the surrounding air by transmitting their vibrations to a larger surface area capable of displacing larger volumes of air (and thus producing louder sounds). This calls for an arrangement that allows for the strings to vibrate freely, but also conducts those vibrations efficiently to the larger surface. A bridge is the customary means by which this is accomplished.
Positioning
Typically, the bridge is placed perpendicular to the strings and larger surface (which are roughly parallel to one another) with the
tensionIn physics, tension is the magnitude of the pulling force exerted by a string, cable, chain, or similar object on another object. It is the opposite of compression. As tension is the magnitude of a force, it is measured in newtons and is always measured parallel to the string on which it applies...
of the strings pressing down on the bridge and thus on the larger surface beneath it. That larger, more acoustically responsive surface may be coupled to a sound chamber — an enclosure such as the body of a
guitarThe guitar is a musical instrument with ancient roots that adapts readily to a wide variety of musical styles. It typically has six strings, but four-, seven-, eight-, ten-, eleven-, twelve-, thirteen- and eighteen-string guitars also exist. The size and shape of the neck and the base of the guitar...
or
violinThe violin is a bowed string instrument with four strings usually tuned in perfect fifths. It is the smallest and highest-pitched member of the violin family of string instruments, which also includes the viola and cello....
— that assists in sound amplification. Depending on the type of stringed instrument, the
resonantIn physics, resonance is the tendency of a system to oscillate at larger amplitude at some frequencies than at others. These are known as the system's resonant frequencies . At these frequencies, even small periodic driving forces can produce large amplitude vibrations, because the system...
surface the bridge rests on may be made of wood, as the top plate of a
guitarThe guitar is a musical instrument with ancient roots that adapts readily to a wide variety of musical styles. It typically has six strings, but four-, seven-, eight-, ten-, eleven-, twelve-, thirteen- and eighteen-string guitars also exist. The size and shape of the neck and the base of the guitar...
or
violinThe violin is a bowed string instrument with four strings usually tuned in perfect fifths. It is the smallest and highest-pitched member of the violin family of string instruments, which also includes the viola and cello....
; of calfskin or plastic, as the head of a
banjoThe banjo is a stringed instrument developed by enslaved Africans in the United States, adapted from several African instruments.The name banjo is commonly thought to be derived from the Kimbundu term mbanza...
; of metal, as on certain types of resophonic fretted instruments; or of virtually any material that vibrates sympathetically with the strings.
Construction
Bridges may consist of a single piece of material, most commonly wood, that fits between the strings and the resonant surface. Alternatively, a bridge may consist of multiple parts. One common form is a bridge that incorporates a separate bearing surface on which the strings rest, termed a
saddle. This is often of a material harder than the bridge itself, such as bone, ivory, high-density plastic, or metal. A classical guitar uses a saddle which sits loosely in the hardwood bridge and is kept there by string tension. The saddle has shallow grooves in it, at least for the treble strings, to prevent them moving around during hard playing.
Yet another type of multipart bridge is common on instruments whose sound plate is curved rather than flat. Instruments of this type, such as arch-top
guitarThe guitar is a musical instrument with ancient roots that adapts readily to a wide variety of musical styles. It typically has six strings, but four-, seven-, eight-, ten-, eleven-, twelve-, thirteen- and eighteen-string guitars also exist. The size and shape of the neck and the base of the guitar...
s and
mandolinA mandolin is a musical instrument in the lute family . It is descended from the mandore, a soprano member of the lute family...
s, often have a bridge comprising a base and a separate saddle that can be adjusted for height.
Operation
The bridge must transfer vibration to the
sound boardThe sounding board or soundboard is the part of a string instrument that transmits the vibrations of the strings to the air, greatly increasing the loudness of sound over that of the string alone....
or other amplifying surface. As the strings are set in motion, it does this by bending to and fro along the string direction, at twice the rate of the string vibration. This causes the sounding board to vibrate at the same frequency as the string producing a wave-like motion and an audible sound.
Bridges are designed to hold the strings at a suitable height above the
fingerboardThe fingerboard is a part of most stringed instruments. It is a thin, long strip of wood that is laminated to the front of the neck of an instrument and above which the strings run...
of the instrument. The ideal bridge height is one that creates sufficient angularity in the string to create enough down force to drive the top but places the strings sufficiently close to the fingerboard to make noting the strings easy. Bridge height may be fixed or alterable.
In addition to supporting the strings and transmitting their vibrations, the bridge also controls the spacing of the strings from one another. This is accomplished by shallow grooves cut in the bridge or its saddle. The strings sit in those grooves and thus are held in their proper lateral position. The nut, situated at the opposite end of the instrument from the bridge or tailpiece (typically where the head holding the tuning pegs joins the fingerboard), serves a similar string-spacing function at the strings' other end.
Be careful as to not glue in the bridge as it will dampen the vibration transfer between the strings and body of the guitar giving the guitar an off sound.
Electric guitar bridges
Bridges for electric guitars can be divided into two main groups, "
tremoloA tremolo arm, tremolo bar or whammy bar is a lever attached to the bridge and/or the tailpiece of an electric guitar or archtop guitar to enable the player to quickly vary the tension and sometimes the length of the strings temporarily, changing the pitch to create a vibrato, portamento or pitch...
" and "non-tremolo" (also called hardtail). Tremolo bridges have an arm (called the tremolo or whammy bar) that extends from below the string anchoring point. It acts as a
leverIn physics, a lever is a rigid object that is used with an appropriate fulcrum or pivot point to multiply the mechanical force that can be applied to another object....
that the player can push or pull to change the strings
tensionIn physics, tension is the magnitude of the pulling force exerted by a string, cable, chain, or similar object on another object. It is the opposite of compression. As tension is the magnitude of a force, it is measured in newtons and is always measured parallel to the string on which it applies...
and, as a result, the
pitchPitch represents the perceived fundamental frequency of a sound. It is one of the three major auditory attributes of sounds along with loudness and timbre. When the actual fundamental frequency can be precisely determined through physical measurement, it may differ from the perceived pitch because...
. This means that this type of bridge produces a
vibratoVibrato is a musical effect, produced in singing and on musical instruments by a regular pulsating change of pitch, and is used to add expression and vocal-like qualities to instrumental music...
rather than tremolo, but the term is deeply entrenched in popular usage. Non-tremolo bridges supply an anchoring point for the strings but provide no active control over string tension or pitch. A small group of tremolo bridges has an extended tail (also called longtail). These guitars have more reverb in their sound, because of the string resonance behind the bridge. The
Fender JaguarThe Fender Jaguar is an electric guitar which was introduced in 1962. Whether the designers of the Jaguar had intended the instrument to be used for Surf music, or if it was a further attempt to break into the Jazz guitar market remains a topic of dispute among Jaguar aficionados...
is a famous example of such a guitar.
All bridges have advantages, depending on the playing style, but, in general, a non-tremolo bridge is thought to provide better tuning stability and a solid contact between the guitar body and the strings.
Tremolo bridges
Generally, the more
contactContact means to touch physically or to communicate with.Contact may also refer to one of the things below.- In social interaction :* Social contact, a person known to an individual, possibly on a different basis than friendship...
the bridge has with the body (i.e. the lower the position), the better the sound transfer will be into the body. A warmer sound with increased sustain is the result.
Tremolo bridges usually need to be suspended in some way, which reduces contact. Most tremolo designs today use a group of
springsA spring is an elastic object used to store mechanical energy. Springs are usually made out of hardened steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after fabrication...
in the guitar body, which oppose the tension of the strings. Some players feel that the vibration of the springs affects
resonanceIn physics, resonance is the tendency of a system to oscillate at larger amplitude at some frequencies than at others. These are known as the system's resonant frequencies . At these frequencies, even small periodic driving forces can produce large amplitude vibrations, because the system...
in a way that makes the guitar sound better; others disagree. Naturally, it all depends on personal preference and the musical style of the individual player.
Since many playing styles make use of a tremolo obligatory, most solid-body guitars today are manufactured with one of two kinds of tremolos:
Non-Locking Tremolo
Non-locking (or vintage) tremolos are the bridges found on all guitars manufactured prior to the advent of the
Floyd RoseFloyd Rose is the organization that licenses, distributes and manufactures the Floyd Rose Locking Tremolo invented by Floyd D. Rose. Floyd Rose owns the patents on the design, and licenses these patents to several original equipment manufacturers....
locking tremolo in the late 1970s and many (typically cheaper) guitars manufactured thereafter. For many playing styles, vintage tremolos are a good choice because they are easy to use and maintain and have very few parts. Some people feel that they can also provide a better degree of sound transfer, especially with tailpiece type tremolos such as the Bigsby. However, "Synchronized Tremolo" type found on the Fender Stratocaster is balanced against a set of screws in much the same manner as a locking tremolo and offers little improvement in the way of sounds transfer. Given that this type of tremolo is installed on solid body guitars the degree to which sound transfer affects the sound that the instrument produces is minimal. Also, keeping a guitar with a non-locking tremolo in tune can be difficult. The most common types of non-locking tremolos are the "Synchronized Tremolo" type and an almost endless stream of copies. The Bigsby vibrato tailpiece is another option, although that type has largely fallen out of favour.
Locking Tremolo
Another type of tremolo is the locking tremolo. These bridges have a sort of vise in each saddle which clamps the string into place (usually with an Allen key). The end of the string has a clamp, which holds the string in place, stopping it from slipping. This is especially useful for songs that require tapping or heavy/hard playing styles. Once set up for tuning stability, locking tremolos are very good. However, their fulcrum points offer extremely minute contact with the body, which may disturb sound transfer.
Non-Tremolo bridges
]
It is generally thought that non-tremolo bridges offer better transfer of string vibration into the body. This is due to direct contact of the bridge to the guitar's body.
These bridges are bolted directly to the guitar body and, assuming good quality, limit longitudinal string movement completely. Therefore tuning stability is assured.
The improved transfer of string vibration into the body has an effect on the sound, so guitars with this type of bridge have different characteristics than those with tremolos even when it is removed. There are no springs in the body or a cavity to accommodate them, which also affects resonance.
See also
- Fingerboard
The fingerboard is a part of most stringed instruments. It is a thin, long strip of wood that is laminated to the front of the neck of an instrument and above which the strings run...
- Electronic tuner
An electronic tuner is a device used by musicians to detect and display the pitch of notes played on musical instruments. The simplest tuners use LED lights or a needle to indicate approximately whether the pitch of the note played is lower, higher, or approximately equal to the desired pitch...
Some tuners attach to the bridge of an instrument.