Capo

A capo (short for capotasto, Italian for "head of fretboard"; /ˈkeɪ.poʊ or ˈkæ.poʊ/) is a device used on the neck of a stringed (typically fretted) instrument to shorten the playable length of the strings, hence raising the pitch. It is frequently used on guitars, mandolins, and banjos. Giovanni Battista Doni first used the term in his Annotazioni of 1640, though capo use likely began earlier in the 17th-century. The first patented capo was designed by James Ashborn of Walcottville, Connecticut, USA.

The capo is most commonly used to raise the pitch of a fretted instrument so that a player can perform a piece in a certain key using different fingerings to what they would use if played "open" (i.e. without a capo). In effect, a capo uses a fret of an instrument to create a new nut at a higher note than the instrument's actual nut. Whatever the style, the capo is typically placed as close to the desired fret as possible, just behind the fret. This holds the strings down behind the fret as securely as possible with the sharpest possible angle to ensure they will remain fretted.

There are numerous styles of capos, but most commercial capos consist of a rubber-covered bar that holds down the strings of the instrument and is clamped to the instrument by one of a number of mechanisms. The same style of capo may be sold in different sizes and shapes for different instruments and fretboard curvatures.

The most relevant mechanical factors that vary by type of capo are their ease/method of use, their size and tendency to interfere with the player's hands, and their ability to hold down the strings uniformly without affecting the tuning of the instrument.

Capos have been used on many other stringed instruments, including relatives of the mandolin (such as the mandola and Greek bouzouki), and four-string banjos. There is a special two-piece capo available for the square-necked Dobro, or resonator guitar, which does not contact the neck, but clamps above and below the strings themselves.