A capo is a small device that clamps onto the neck of a guitar or other fretted stringed instrument and shortens the length of the strings, raising their pitch. It is usually fastened across all the strings of a guitar, although less often it can be used on only some strings rather than all of them. The main advantage of using a capo is that it lets a guitarist play a song in different keys while still using first-position open-string chord forms, which have a more droning and fully resonant tone than many bar chords. A capo functions as a sort of moveable nut, as it can be affixed to any fret below the neck joint and provide the same kind of vibration termination. By doing this, it changes the pitch and key of the whole guitar, meaning that the chord shapes you have learned can still be used higher up on the fretboard. The chords played will be different, but the chord progressions you have learned will still sound good. Capos can also be useful for singers in the sense that they can shift the key up to a scale that suits the vocalist. Capos are a vital tool for any guitarist, and they can be used as a creative tool to create songs.