A string under tension will vibrate when plucked, bowed or hit. String instruments are as old as music history. The earliest strings were probably strips of sun-dried animal skins or guts. Metal and nylon strings are found on modern instruments. Plucking produces sounds on the banjo, guitar, harp, lute, mandolin, and sitar. Harpsichord strings are plucked by a mechanical device, unlike the piano which uses hammers to strike the string. Orchestral stings are bowed for sustained sounds and plucked for staccato sounds (pizzicato).
The pitch of a vibrating string depends on three factors:
The length of the string: longer string = lower pitch; shorter =higher pitch. Frequency is inversely proportional to the length. A string twice as long will produce a tone of half the frequency (one octave lower).
Tension: less tension (looser) = lower pitch; greater tension (tighter) = higher pitch. The frequency is proportional to the square root of the tension. If the string is too lose, it won't play. If the string is too tight, it will break. The middle path the right way.
Density: Thicker, heavier strings vibrate more slowly that finer lighter strings. Frequency is inversely proportional to the square root of the density:
In practice, string instruments are tuned by adjusting tension. The strings are supplied with the right density and length to achieve the desirable range of frequencies. Pitch changes are determined by finger pressure against on the string against the finger board which changes the length.
Tunings for string instruments:
violin G, D, A, E
viola, cello, tenor banjo, mandolin C, G, D, A
double bass, bass guitar E, A, D, G
guitar E, A, D, G, B, E
Some string instruments such as the violin have an open finger board and others such as the guitar have frets, raised ridges perpendicular to the strings, usually arranged at semitone intervals. Modern frets are metal, set into slots in the fretboard. A violinist presses a string firmly against the fingerboard with the fingers of the left hand to change the pitch. In addition, the pressing finger is vibrated to produce vibrato when the note is sustained. Years of practice are required to develop accurate pitch control with pleasing vibrato on the violin, viola, cello and bass violin. In contrast, a fret board automatically determines the pitch of a pressed string; the player simply presses the right space between frets. The string cannot be vibrated in the manner of a violin.
Many string instruments have been modified for electronic amplification and recording. Piezoelectric or magnetic pickups are placed under the strings to convert vibrations into electrical signals. The instrument is plugged into a mixer and amplifier. Sound effect modules can be inserted into the electrical connection to modify the sound. Electric guitar players use pedal activated effects such as distortion ( should be banned) , reverb, termulo, wah-wah. Bass- electric guitars have replaced the bass violin in jazz, rock and pop music bands.