The flute is a transverse (or side-blown) woodwind instrument that is closed at the blown end. It is played by blowing a stream of air over the embouchure hole. The pitch is changed by opening or closing keys that cover circular tone holes (there are typically 16 tone holes). Opening and closing the holes produces higher and lower pitches. Higher pitches can also be achieved through over-blowing, like most other woodwind instruments. The direction and intensity of the airstream also affects the pitch, timbre, and dynamics.