A reed pipe is an organ pipe

Organ pipe

An organ pipe is a sound-producing element of the pipe organ that resonates at a specific pitch when pressurized air is driven through it. Each pipe is tuned to a specific note of the musical scale...

 that is sounded by a vibrating brass

Brass

Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.In comparison, bronze is principally an alloy of copper and tin...

 strip known as a reed. Air under pressure (referred to as wind) is directed towards the reed, which vibrates at a specific pitch

Pitch (music)

Pitch is an auditory perceptual property that allows the ordering of sounds on a frequency-related scale.Pitches are compared as "higher" and "lower" in the sense associated with musical melodies,...

. This is in contrast to flue pipe

Flue pipe

A flue pipe is an organ pipe that produces sound through the vibration of air molecules, in the same manner as a recorder or a whistle. Air under pressure is driven down a flue and against a sharp lip called a Labium, causing the column of air in the pipe to resonate at a frequency determined by...

s, which contain no moving parts and produce sound solely through the vibration of air molecules. Reed pipes are common components of pipe organ

Pipe organ

The pipe organ is a musical instrument that produces sound by driving pressurized air through pipes selected via a keyboard. Because each organ pipe produces a single pitch, the pipes are provided in sets called ranks, each of which has a common timbre and volume throughout the keyboard compass...

s.

Construction

A reed pipe comprises a metal tongue (the reed) which rests against a shallot, in which is carved a tunnel. The reed and shallot are held in place by a wooden wedge. This assembly protrudes from the underside of the block and hangs down into the boot. A tuning wire is inserted though the boot and is bent to hold the reed against the shallot. The wire is moved up or down using a tuning knife in order to change the length of the tongue that is permitted to vibrate, thereby changing the pitch produced by the pipe. The resonator joins with the upper opening of the shallot and extends above the boot. The resonator may be made in a wide variety of lengths, shapes, and configurations, depending on the desired tone quality.

Actuation

As wind enters the boot, it travels over the reed, causing it to vibrate against the shallot. This produces the pipe's sound. The wind passes through the shallot and up into the resonator, which focuses and refines the sound wave produced by the reed.

Free reeds

A less-common type of reed construction is the free reed. The term refers to two types of reeds where the tongue does not beat directly against the shallot in order to produce the reed tone, which creates a unique sound (these are most commonly used on nineteenth-century German or French organs). In one case, the free reed stop will appear from the outside like a normal reed (complete with boot, tuning wire, and resonator, etc.). The only difference lies in the action of the tongue (see above), which beats "through" the shallot (hence the German term for the reed--durchschlagend). In the other form of the reed, an enclosed boot does not exist (as in normal reed pipes); therefore, all the tongues are held together in the same chamber, as in the harmonica

Harmonica

The harmonica, also called harp, French harp, blues harp, and mouth organ, is a free reed wind instrument used primarily in blues and American folk music, jazz, country, and rock and roll. It is played by blowing air into it or drawing air out by placing lips over individual holes or multiple holes...

, accordion

Accordion

The accordion is a box-shaped musical instrument of the bellows-driven free-reed aerophone family, sometimes referred to as a squeezebox. A person who plays the accordion is called an accordionist....

, or harmonium

Harmonium

A harmonium is a free-standing keyboard instrument similar to a reed organ. Sound is produced by air being blown through sets of free reeds, resulting in a sound similar to that of an accordion...

. This arrangement makes it possible to change the volume produced without changing its pitch by varying the wind pressure, which is not possible with normal organ pipes. This type of free reed was popular among certain organ builders of the nineteenth century due to the increased interest in a more expressive aesthetic. Volume adjustment was available to the organist

Organist

An organist is a musician who plays any type of organ. An organist may play solo organ works, play with an ensemble or orchestra, or accompany one or more singers or instrumental soloists...

 by means of a balanced expression pedal

Expression pedal

An expression pedal is an important control found on many organs and synthesizers, as well as in the pedal steel guitar, that allows the volume of the sound to be manipulated...

 which varied the wind pressure delivered to the free reed stop.

Tonal characteristics

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

Timbre

In music, timbre is the quality of a musical note or sound or tone that distinguishes different types of sound production, such as voices and musical instruments, such as string instruments, wind instruments, and percussion instruments. The physical characteristics of sound that determine the...

. 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. 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).

External links

• Encyclopedia of Organ Stops