In the world of music, what is a "fipple"?

The mouthpiece of a recorder shows a wooden block (A) with a channel carved into the body of the instrument (B), together forming a duct that directs a ribbon of air across an opening toward a sharp edge (C). The edge splits the air in a manner that alternately directs it into and outside of the tube, setting the contained column of air into periodic vibration. This flow-controlled "air reed" is a definitive characteristic of all flutes, which therefore all have an edge or equivalent air-splitting device.