Fret buzz

A fret is a raised element on the neck of a stringed instrument. Frets usually extend across the full width of the neck. On most modern western fretted instruments, frets are metal strips inserted into the fingerboard. On some historical instruments and non-European instruments, frets are made of pieces of string tied around the neck.

Frets divide the neck into fixed segments at intervals related to a musical framework. On instruments such as guitars, each fret represents one semitone in the standard western system, in which one octave is divided into twelve semitones. Fret is often used as a verb, meaning simply "to press down the string behind a fret". Fretting often refers to the frets and/or their system of placement.

Pressing the string against the fret reduces the vibrating length of the string to that between the bridge and the next fret between the fretting finger and the bridge. This is damped if the string were stopped with the soft fingertip on a fretless fingerboard.

Frets make it much easier for a player to achieve an acceptable standard of intonation, since the frets determine the positions for the correct notes. Furthermore, a fretted fingerboard makes it easier to play chords accurately.

A disadvantage of frets is that they restrict pitches to the temperament defined by the fret positions. A player may still influence intonation, however, by pulling the string to the side to increase string tension and raise the pitch. This technique (commonly called 'bending') is often used by electric guitarists of all genres, and is an important part of sitar playing. On instruments with frets that are thicker off the fingerboard, string tension and pitch vary with finger pressure behind the fret. Sometimes a player can pull the string toward the bridge or nut, thus lowering or raising the string tension and pitch. However, except for instruments that accommodate extensive string pulling, like the sitar, much less influence on intonation is possible than on unfretted instruments.

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Wikipedia