A string instrument (or stringed instrument) is a musical instrument that produces sound by means of vibrating strings. In the Hornbostel-Sachs scheme of musical instrument classification, used in organology, they are called chordophones. The most common string instruments in the string family are guitar, violin, viola, cello, double bass, banjo, mandolin, ukulele, harpsichord and harp.
TYPES OF STRING INSTRUMENTS
Construction
String instruments can be divided in three groups.
◘Lutes - instruments in which the strings are supported by a neck and a bout ("gourd"), for instance a guitar, a violin, a saz.
◘Harps - instruments in which the strings are contained within a frame.
◘Zithers - instruments with the strings mounted on a body, such as a guqin, a cimbalom, an autoharp, or a piano.
It is also possible to divide the instruments in groups focused on how the instrument is played.
TYPES OF PLAYING TECHNIQUE
All string instruments produce sound from one or more vibrating strings, transferred to the air by the body of the instrument (or by a pickup in the case of electronically amplified instruments). They are usually categorized by the technique used to make the strings vibrate (or by the primary technique, in the case of instruments where more than one may apply.) The three most common techniques are plucking, bowing and striking.
Plucking
Plucking is used as the sole method of playing on instruments such as the banjo, guitar, harp, lute, mandolin, oud, sitar, and either by a finger or thumb, or by some type of plectrum. This category includes the keyboard instrument the harpsichord, which formerly used feather quills (now plastic plectra) to pluck the strings.
Instruments normally played by bowing (see below) may also be plucked, a technique referred to by the Italian term pizzicato.
Bowing
Bowing (Italian: Arco) is a method used in some string instruments, including the violin, viola, cello, and the double bass (of the violin family) and the old viol family. The bow consists of a stick with many hairs stretched between its ends. Bowing the instrument's string causes a stick-slip phenomenon to occur, which makes the string vibrate.
Ancestors of the modern bowed string instruments are the rebab of the Islamic Empires, the Persian kamanche and the Byzantine lira. Other bowed instruments are the rebec, hardingfele, nyckelharpa, kokyū, erhu, igil, sarangi and K'ni. The hurdy gurdy is bowed by a wheel.
Rarely, the guitar can be played with a bow (rather than plucked) for unique effects.
Striking
The third common method of sound production in stringed instruments is to strike the string.
Violin family string instrument players are occasionally instructed to strike the string with the side of the bow, a technique called col legno. This yields a percussive sound along with the pitch of the note. A well-known use of col legno for orchestral strings is the Gustav Holst's "Mars" movement from The Planets suite.
Other methods
The aeolian harp employs a very unusual method of sound production: the strings are excited by the movement of the air.
Some string instruments have keyboards attached which are manipulated by the player, meaning they do not have to pay attention to the strings directly. The most familiar example is the piano, where the keys control the felt hammers by means of a complex mechanical action. Other string instruments with a keyboard include the clavichord (where the strings are struck by tangents), and the harpsichord (where the strings are plucked by tiny plectra).
With these keyboard instruments too, the strings are occasionally plucked or bowed by hand. Composers such as Henry Cowell wrote music which asks for the player to reach inside the piano and pluck the strings directly, or to "bow" them with bow hair wrapped around the strings, or play them by rolling the bell of a brass instrument such as a trombone on the array of strings.
Other keyed string instruments, small enough to be held by a strolling player, include the plucked autoharp, the bowed nyckelharpa, and the hurdy gurdy, which is played by cranking a rosined wheel.
Steel-stringed instruments (such as the guitar, bass, violin, etc.) can be played using a magnetic field. An E-Bow is small hand-held battery-powered device which can be used to excite the strings of an electric guitar. It provides a sustained, singing tone on the string which is magnetically vibrated.
3rd Bridge is a plucking method where the string is divided in two pieces and struck at the side which is unamplified. The technique is mainly used on electric instruments, because these have a pickup which amplifies only the local string vibration. It's possible on acoustic instruments as well, but lesser convenient. For instance press on the 7th fret on a guitar and pluck it at the head side and a tone will resonate at the opposed part. At electric instruments this technique can generate multitone sounds remniscent of a clock or a bell.
