The end-blown flute (also called an edge-blown flute or rim-blown flute) is a keyless woodwind instrument played by directing an airstream against the sharp edge of the upper end of a tube. Unlike a recorder or tin whistle, there is not a ducted flue voicing, also known as a fipple. Most rim-blown flutes are "oblique" flutes, being played at an angle to the body's vertical axis. They generate sound by at this end blown voicing by siphon effect. A notched flute is an end-blown flute with a notch on the blowing surface. A lip-valley flute is a type of notched flute.