Capo

A clamp that presses the strings down against a fret, raising the pitch of the whole instrument so open shapes can be played in another key.

It works by shortening the speaking length at a chosen fret, so every open chord shape simply transposes. Spring, screw and cam mechanisms all exist, and the important quality is even pressure: too much and the strings go sharp and the neck is pulled, too little and the bass strings buzz. Radius-matched clamps sit better on strongly curved fingerboards, and a partial capo covering only some strings creates open-tuned effects without retuning.

Example: clamping at the second fret and playing G shapes puts the song in A, which is how a singer's key is matched without a retune between songs.

Capo

See also