The Jew's harp, jaw harp, mouth harp, or Ozark harp and juice harp, is thought to be one of the oldest musical instruments in the world, it is thought as old as the 4th century BC. To play the Jaw Harp the tongue/reed is placed in the performer's mouth and plucked with the finger to produce a note. The frame is held firmly against the performer's parted front teeth, using the jaw (thus "jaw harp") and mouth as a resonator, greatly increasing the volume of the instrument. The teeth must be parted sufficiently for the reed to vibrate freely and the fleshy parts of the mouth should not come into contact with the reed to prevent damping of the vibrations. The note thus produced is constant, though by changing the shape of his or her mouth and the amount of air contained in it, the performer can make higher or lower pitch sounds and thus create melodies. The volume of the note can be varied by breathing in and out.