The nut of a string instrument

String instrument

A string 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...

 is a small piece of hard material which supports the strings

Strings (music)

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 kept under tension so that they may vibrate freely, but controllably. Strings may be "plain"...

 at the end closest to the headstock

Headstock

Headstock or peghead is a part of guitar or similar stringed instrument. The main function of a headstock is holding the instrument's strings. Strings go from the bridge past the nut and are usually fixed on machine heads on headstock...

 or scroll

Scroll (music)

A scroll is the decoratively carved end of the neck of certain stringed instruments, mainly members of the violin family. The scroll is typically carved in the shape of a volute according to a canonical pattern, although some violins are adorned with carved heads, human and animal. The quality of...

. The nut marks one end of the speaking length of each open string, sets the spacing of the strings across the neck, and usually holds the strings at the proper height from the fingerboard

Fingerboard

The fingerboard is a part of most stringed instruments. It is a thin, long strip of material, usually wood, that is laminated to the front of the neck of an instrument and above which the strings run...

. Along with the bridge

Bridge (instrument)

A bridge is a device for supporting the strings on a stringed instrument and transmitting the vibration of those strings to some other structural component of the instrument in order to transfer the sound to the surrounding air.- Explanation :...

, the nut defines the vibrating lengths (scale lengths) of the open strings.
The nut may be made of ebony

Ebony

Ebony is a dense black wood, most commonly yielded by several species in the genus Diospyros, but ebony may also refer to other heavy, black woods from unrelated species. Ebony is dense enough to sink in water. Its fine texture, and very smooth finish when polished, make it valuable as an...

, ivory

Ivory

Ivory is a term for dentine, which constitutes the bulk of the teeth and tusks of animals, when used as a material for art or manufacturing. Ivory has been important since ancient times for making a range of items, from ivory carvings to false teeth, fans, dominoes, joint tubes, piano keys and...

, cow bone, brass

Brass

Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.In comparison, bronze is principally an alloy of copper and tin...

, Corian

Corian

Corian is the brand name for a solid surface material created by DuPont. It is composed of acrylic polymer and alumina trihydrate. Corian can be thermoformed by heating it to 300°F , allowing unique shapes to be created...

 or plastic, and is usually notched or grooved for the strings. The grooves are designed to lead the string from the fingerboard to the headstock or pegbox in a smooth curve, to prevent damage to the strings or their windings. Bowed string instruments in particular benefit from an application of soft pencil graphite in the notches of the nut, to preserve the delicate flat windings of their strings.

Etymology

The word is thought to have come from the German Nut , meaning "groove" or "slot".

Variations

Not all string instruments have nuts as described:

• Some guitars and mandolins, for example, have nuts that are just string spacers, with deep notches. These instruments use a zero fret
  Zero fret
  A zero fret is a fret placed at the headstock end of the neck of a banjo, guitar, mandolin, or bass guitar. It serves one of the functions of a nut: holding the strings the correct distance above the other frets on the instrument's fretboard...
  
  , which is a fret
  Fret
  A fret is a raised portion on the neck of a stringed instrument, that extends generally across the full width of the neck. On most modern western instruments, frets are metal strips inserted into the fingerboard...
  
   at the beginning of the scale where a normal nut would be, which is higher than the other frets to provide the correct string clearance. The zero fret is often found on cheaper instruments, as it's much easier to set up an instrument this way; to make a proper nut requires that each string notch be carefully cut to the proper depth so that the string is neither too high, affecting overall string height and intonation of fretted notes, nor too low which causes a plucked or picked string to buzz against the frets. With a zero fret, the fret merely needs to be the right height. However, a zero fret also makes the sound of the open string very similar to the fretted note, where the nut itself, being made of a different material, has a different timbre if it is used instead of a zero fret. It is thus used for this reason on some high-end instruments.:

• The erhu
  Erhu
  The erhu is a two-stringed bowed musical instrument, more specifically a spike fiddle, which may also be called a "southern fiddle", and sometimes known in the Western world as the "Chinese violin" or a "Chinese two-stringed fiddle". It is used as a solo instrument as well as in small ensembles...
  
  does not use a hard nut to define the speaking length of the open string, but rather a qiān jin (千斤) : a loop of string, or, less commonly, a metal hook.