A capo, short for capo d’astro, capo tasto or capotasto [kapoˈtasto], Italian for “head of fretboard”; Spanish, capodastro [ka.po’ðas.tɾo]; French, capodastre; German, Kapodaster; Portuguese, capodastro) 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.
Playing with a capo creates the same musical effect as retuning all strings up the same number of steps. However, using a capo only affects the open note of each string. Every other fret remains unaffected (e.g., the 7th fret of an E-string still plays a B note for any capo position at or below the 7th fret), and thus a performer does not need to adjust for or relearn the entire fretboard as they might with retuning. The scale length of the strings of an instrument affects the timbre of the strings, and thus the use of a capo may alter the tone of the instrument.
There is no record of who invented the capo, although Giovanni Battista Doni of Italy was the first to record the term in 1640. And James Ashborn of America was the the first to apply for a capo-related patent in 1850.
Different styles of capos are affixed to a guitar neck just behind the fret wire by one of several different attachment methods. Most have a rubber-covered bar that actually holds down the strings, fastened to the neck with an elastic, nylon or other fabric strap; or by a spring, screw or cam-operated clamp.
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