Fipple flute

A fipple is a constricted mouthpiece common to many end-blown flutes, such as the tin whistle and the recorder. These instruments are known variously as fipple flutes, duct flutes, or tubular-ducted flutes.

In the accompanying illustration of the head of a recorder, the wooden fipple plug (A), with a "ducted flue" windway above it in the mouthpiece of the instrument, compresses the player's breath, so that it travels along the duct (B), called the "windway". Exiting from the windway, the breath is directed against a hard, bladed edge (C), called the "labium lip" or windcutter, producing a Bernoulli effect or siphon. The air flowing over the voicing mouth creates a flow-controlled valve, or "air reed." Interaction between the air reed and the air column in the body of the instrument excites standing waves in the air column, which determines the pitch of the sound. This oscillation results in the "whistle sound" in ducted flue instruments. See wind instrument and flue pipe. A distinct tone color, determined by the dimensions of the instrument and the voicing mouth, is then slightly modified by the player's technique or embouchure. In instruments such as the recorder, the player can vary the pitch of the resulting musical note by opening or closing finger holes along the bore of the instrument, thus changing the effective length.

The windway consists of the "wind canal" or "flue", the upper portion of the voicing/mouth as carved into the headjoint itself, and the ducted flue windway, as carved onto the top surface of the fipple block. The space created between the ducted flue windway and the labium ramp edge is referred to as the "mouth" or "voicing".

The size of the mouth (length, width and depth) is usually in proportion to the instrument's bore, depending on the model of instrument and specifically which original instrument is being copied (in the cases of recorders). Many mass-produced factory instruments feature a voicing of a rectangular or flat lozenge cross section. Such a flat and rectangular voicing however, produces a less-than-sweet tone and offers far less dynamic flexibility (pitch bending) than a flute embouchure. The recorder voicing was designed to limit pitch bending for a more stable tone with variations in breath pressure. Typically, a shallow ramp instrument, such as a tabor pipe, will allow faster register changes, pitch bending and "flutey" tone, while an instrument with a deeper ramp will limit fast register changes, pitch bending and produce a more "reedy" tone.

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