The long-string instrument is a musical instrument in which the string is of such a length that the fundamental transverse wave is below what a person can hear as a tone (±20 Hz). If the tension and the length result in sounds with such a frequency, the tone becomes a beating frequency that ranges from a short reverb (approx 5–10 meters) to longer echo sounds (longer than 10 meters). Besides the beating frequency, the string also gives higher pitched natural overtones. Since the length is that long, this has an effect on the attack tone. The attack tone shoots through the string in a longitudinal wave and generates the typical science-fiction laser-gun sound as heard in Star Wars .  The sound is also similar to that occurring in upper electricity cables for trains.
A long string instrument was one of the techniques by which Mersenne tested Galileo's hypothesis, now known under Mersenne's name, by making string vibration speed visible and countable.  For example if a string 0.33 meters long, of given mass and tension, produces A440, a string with identical mass and tension but eight times as long, 2.64 meters, produces 55 hertz.
One example of a long-string instrument was invented by the American composer Ellen Fullman. It is tuned in just intonation  and played by walking along the length of its approximately 100 90-foot (27 m)-long strings and rubbing them with rosined hands and producing longitudinal vibrations. A C-clamp is used on each string for putting tension on the strings, much like a guitar capo, and a resonator is placed on the end the musician faces. This long-string instrument's range is centered on the octave of middle C[ citation needed ] and extends above and below this by an octave. The strings of the bass octave extend the instrument's full 90 feet.
Fullman is not the only person who has built long-string instruments. Alvin Lucier employed a monochord of up to 25 meters in his piece Music on a Long Thin Wire (1977).  In 1981 Terry Fox also recorded two musical pieces called Berlin Attic Wire, Beating with a long string instrument.  Since 1983, in addition to his work on and about the violin, Jon Rose has been bowing and recording the music of fences worldwide.  Throughout his career Paul Panhuysen made many large sound installations with groups of long strings.  George Smits built long string instruments acoustically amplified with styrofoam.
The experimental luthier and recording artist Yuri Landman built a portable electric long-string instrument.  A three-minute solo that he recorded in a garden on this instrument can be heard on YouTube, uploaded in 2011. 
Sound lab and research centre Sonoscopia in Porto, Portugal has a permanent electric amplified long-string instrument mounted to the wall in the hall of their building.
The guitar is a fretted musical instrument that typically has six strings. It is usually held flat against the player's body and played by strumming or plucking the strings with the dominant hand, while simultaneously pressing selected strings against frets with the fingers of the opposite hand. A plectrum or individual finger picks may also be used to strike the strings. The sound of the guitar is projected either acoustically, by means of a resonant chamber on the instrument, or amplified by an electronic pickup and an amplifier.
In music, there are two common meanings for tuning:
The piano is a stringed keyboard instrument in which the strings are struck by wooden hammers that are coated with a softer material. It is played using a keyboard, which is a row of keys that the performer presses down or strikes with the fingers and thumbs of both hands to cause the hammers to strike the strings. It was invented in Italy by Bartolomeo Cristofori around the year 1700.
An overtone is any resonant frequency above the fundamental frequency of a sound. In other words, overtones are all pitches higher than the lowest pitch within an individual sound; the fundamental is the lowest pitch. While the fundamental is usually heard most prominently, overtones are actually present in any pitch except a true sine wave. The relative volume or amplitude of various overtone partials is one of the key identifying features of timbre, or the individual characteristic of a sound.
String instruments, stringed instruments, or chordophones are musical instruments that produce sound from vibrating strings when a performer plays or sounds the strings in some manner.
In music, inharmonicity is the degree to which the frequencies of overtones depart from whole multiples of the fundamental frequency.
Piano acoustics is the set of physical properties of the piano that affect its sound. It is an area of study within musical acoustics.
Ellen Fullman is an American composer, instrument builder, and performer. She was born in Memphis, Tennessee, and is currently based in the San Francisco Bay Area. She is known for her 70-foot (21-meter) Long String instrument, tuned in just intonation and played with rosin-coated fingers.
A monochord, also known as sonometer, is an ancient musical and scientific laboratory instrument, involving one string. The term monochord is sometimes used as the class-name for any musical stringed instrument having only one string and a stick shaped body, also known as musical bows. According to the Hornbostel–Sachs system, string bows are bar zithers (311.1) while monochords are traditionally board zithers (314). The "harmonical canon", or monochord is, at its least, "merely a string having a board under it of exactly the same length, upon which may be delineated the points at which the string must be stopped to give certain notes," allowing comparison.
An electric violin is a violin equipped with an electronic output of its sound. The term most properly refers to an instrument intentionally made to be electrified with built-in pickups, usually with a solid body. It can also refer to a violin fitted with an electric pickup of some type, although "amplified violin" or "electro-acoustic violin" are more accurate then.
A prepared guitar is a guitar that has had its timbre altered by placing various objects on or between the instrument's strings, including other extended techniques. This practice is sometimes called tabletop guitar, because many prepared guitarists do not hold the instrument in the usual manner, but instead place the guitar on a table to manipulate it.
Piano tuning is the act of adjusting the tension of the strings of an acoustic piano so that the musical intervals between strings are in tune. The meaning of the term 'in tune', in the context of piano tuning, is not simply a particular fixed set of pitches. Fine piano tuning requires an assessment of the vibration interaction among notes, which is different for every piano, thus in practice requiring slightly different pitches from any theoretical standard. Pianos are usually tuned to a modified version of the system called equal temperament.
A string is the vibrating element that produces sound in string instruments such as the guitar, harp, piano, and members of the violin family. Strings are lengths of a flexible material that a musical instrument holds under tension so that they can vibrate freely, but controllably. Strings may be "plain", consisting only of a single material, like steel, nylon, or gut, or wound, having a "core" of one material and an overwinding of another. This is to make the string vibrate at the desired pitch, while maintaining a low profile and sufficient flexibility for playability.
Stretched tuning is a detail of musical tuning, applied to wire-stringed musical instruments, older, non-digital electric pianos, and some sample-based synthesizers based on these instruments, to accommodate the natural inharmonicity of their vibrating elements. In stretched tuning, two notes an octave apart, whose fundamental frequencies theoretically have an exact 2:1 ratio, are tuned slightly farther apart. "For a stretched tuning the octave is greater than a factor of 2; for a compressed tuning the octave is smaller than a factor of 2."
Acoustic resonance is a phenomenon in which an acoustic system amplifies sound waves whose frequency matches one of its own natural frequencies of vibration.
An acoustic guitar is a musical instrument in the string family. When a string is plucked, its vibration is transmitted from the bridge, resonating throughout the top of the guitar. It is also transmitted to the side and back of the instrument, resonating through the air in the body, and producing sound from the sound hole. The original, general term for this stringed instrument is guitar, and the retronym 'acoustic guitar' distinguishes it from an electric guitar, which relies on electronic amplification. Typically, a guitar's body is a sound box, of which the top side serves as a sound board that enhances the vibration sounds of the strings. In standard tuning the guitar's six strings are tuned (low to high) E2 A2 D3 G3 B3 E4.
An experimental musical instrument is a musical instrument that modifies or extends an existing instrument or class of instruments, or defines or creates a new class of instrument. Some are created through simple modifications, such as cracked drum cymbals or metal objects inserted between piano strings in a prepared piano. Some experimental instruments are created from household items like a homemade mute for brass instruments such as bathtub plugs. Other experimental instruments are created from electronic spare parts, or by mixing acoustic instruments with electric components.
Violin acoustics is an area of study within musical acoustics concerned with how the sound of a violin is created as the result of interactions between its many parts. These acoustic qualities are similar to those of other members of the violin family, such as the viola.
Sympathetic resonance or sympathetic vibration is a harmonic phenomenon wherein a passive string or vibratory body responds to external vibrations to which it has a harmonic likeness. The classic example is demonstrated with two similarly-tuned tuning forks. When one fork is struck and held near the other, vibrations are induced in the unstruck fork, even though there is no physical contact between them. In similar fashion, strings will respond to the vibrations of a tuning fork when sufficient harmonic relations exist between them. The effect is most noticeable when the two bodies are tuned in unison or an octave apart, as there is the greatest similarity in vibrational frequency. Sympathetic resonance is an example of injection locking occurring between coupled oscillators, in this case coupled through vibrating air. In musical instruments, sympathetic resonance can produce both desirable and undesirable effects.
Mersenne's laws are laws describing the frequency of oscillation of a stretched string or monochord, useful in musical tuning and musical instrument construction.