Reed pipes produce sound by means of a steady stream of wind passing through a slot in the shallot, and entering the resonator of the pipe. A thin springy piece of metal (brass or phosphor-bronze) called a reed tongue (or, simply, tongue) is attached over the shallot. The tongue is carefully given a slight curvature during the voicing process. When the note is played, air passes through the slot in the shallot, causing the reed to vibrate, thus interrupting the flow of air into the resonator and creating a musical note.
The lengths of both the reed and shallot can be adjusted to regulate and tune the pipe. A further technique used in voicing higher pressure reeds is the addition of a small weight, either screwed or glued to the tongue, in order to promote stability of speech.
Reed pipes are generally made of metal, although the resonators of some heavy bass pipes may be made of wood. The tone is dependent on a multiplicity of parameters connected with the reed, the shallot and the resonator. The reed-voicer’s art is therefore one of the most important specialisations in organbuilding.
The shape of the resonator, and its proportion of length to width, is also critical to the tone of the pipe. The multiplicity of different shapes can be seen in the photogaphs under the different categories of reed pipe.
D: Reed tongue
E: Tuning wire
H: Toe hole