A part of a mouthpiece from an edge-blown aerophone. The fipple is a block or plug inside the mouthpiece below the opening that blocks the flow of air and directs it through a flue or duct (often called a windway) so it can pass over the sharp edge of the lip (often called a labium) causing the air column to split and vibrate to create a pitch.Instruments that employ the use of fipples include: duct flutes, whistle flutes, block flutes, and fipple-flutes.the block of wood which directs the flow of air, by plugging the mouthpiece, in a woodwind instrument of the recorder family, known as fipple flute (or whistle flute). examples of fipple flutes include the recorder, flageolet, and tin or penny whistle