A reed pipe (also referred to as a lingual pipe) is an organ pipe that is sounded by a vibrating brass strip known as a reed. Air under pressure (referred to as wind) is directed towards the reed, which vibrates at a specific pitch. This is in contrast to flue pipes, which contain no moving parts and produce sound solely through the vibration of air molecules. Reed pipes are common components of pipe organs.
The tonal characteristics of reed pipes are determined by several factors, the most important of which is the interaction between the shallot and the tongue. The thickness and curve of the tongue itself play an important role in determining the tonal quality of the pipe. When voicing a reed pipe, the voicer will take great care in shaping the curve of the tongue, because this controls how the tongue beats against the shallot. Whether the shallot is cylindrical or tapered (and, in the latter case, whether or not the taper is inverted) greatly affects the pipe's timbre. Likewise, the "cut" (referring to the depth of the shallot and the shape of the opening) and the closed-end shape (whether the closed end of the shallot is flat, domed, or "Schiffschen") determine whether the tone is more Baroque or more Romantic. In addition, the type of block (whether a standard shape or a French "double-block") in which the reed assembly is set has an effect on the sound.
Scaling is important when determining the final tone color of a reed pipe, though it is not of primary importance as it is in flue pipe construction. This is because reed pipe resonators simply reinforce certain partials of the sound wave; the air column inside the resonator is not the primary vibrator. Likewise, the material out of which the resonator is constructed does not matter as much as it does in flue pipes. The shape of the resonator, however, is quite important: an inverted-conical resonator (such as is typical with a Trumpet rank) produces more harmonics than does a cylindrical resonator (like that of a Clarinet rank).