A saxophone has a conical metal (originally brass) tube with about 24 openings controlled by padded keys; the mouthpiece is similar to that of a clarinet. two octave key vents allow the instrument to overblow to a higher register at the octave. except for the sopranino and one form of the b♭ soprano saxophone, built straight like a clarinet, saxophones have an upturned lower end and a detachable crook, or neck, at the upper end.