Comes from the Italian phrase 'capo dastro' and means 'head of fingerboard'. A capo is a device that clamps onto the fret bars and raises the pitch of all the strings. It allows open strings to be used in other keys, therefore allowing sounds that are not normally possible. Capos also lower the action of the strings and shorten the scale length. A shorter scale length produces a different timbre, one that is similar to that of a shorter stringed instrument.