The sounds of reed pipes are generally stronger in the amount of sound they produce and more varied in timbre than sounds produced by flue pipes. In general the amount of overtone development is greater in reeds than in flues. As might be expected, the differences between the two classes of timbre are rooted in the differences in their construction:
Like flues, reeds can be classified in various ways, reflecting their timbre and/or construction. Classifications based on the construction of reed pipes may be made on the basis of any one of several physical characteristics, described in detail below. On the basis of their use alone, reeds can be classified as either solo reeds or chorus reeds . It cannot be stressed enough, however, that no reed is without some use as either solo or chorus stop, depending on the musical demands of a given situation.
Solo reeds have distinctive names that most often derive from the names of orchestral instruments. Their sounds are particularly useful for playing solo melody lines accompanied by the sounds of other stops, usually flues. Even this classification is flexible, however, for almost any solo reed, particularly some oboes, can also be used to some extent as a part of an ensemble, or even in an accompanimental role. Solo reed sounds can be found on any division of the organ, including the Pedal. Some of the most common solo reeds are
Two different solo reed sounds are represented by short recordings:
- 8' Hautbois
- For Mac users: file in .AIF format
- For PC users: file in .WAV format
- 8' Cromorne
- For Mac users: file in .AIF format
- For PC users: file in .WAV format
Chorus reeds, on the other hand, have a greater use in adding strength and character to a combination of other stops, usually flues. Like solo reeds, they are found in both manual and pedal divisions, but some, including the Trombone (Ger. Posaune) are most often in pedal divisions, where they provide a powerful sound in the bass register. Other stops are more commonly found in manual divisions. Such stops, for both manual and pedal divisions, include
Chorus reeds are most often used in combination with other stops rather than alone. The sound is represented by a short recording of a reed chorus that includes a Trompette 8', Basson 16', Trompette harmonique 8', Clairon 4', and Bombarde 16'.
- For Mac users: file in .AIF format
- For PC users: file in .WAV format
The most important parts of a
reed pipe,
determining both timbre and pitch, is found within the boot, in the shallot
and
tongue. A shallot serves a
purpose similar to that found in woodwind instruments like the clarinet, where a thin
slice of cane
- - the reed - - is attached to a mouth piece and secured with an armature. In the
case of reed
pipes, the shallot is analogous to the mouthpiece, and the tongue to the reed. The
wire
and the wedge hold the tongue against the shallot, serving the same function
as the
armature on a clarinet.
Most shallots look basically alike: they are brass tubes with one flat face into which an opening is cut. The photograph shows two shallots, each one from a reed pipe of a different timbre. Differences in details of the shape of the shallot can be seen, and the differences in shape of both the shallot itself and its opening have an effect on timbre.
The differences seen in the photograph above represent those that are typically found in the two basic types of shallots:
A wider aperture in an open shallot allows more sound to be produced, and also permits a greater development of the fundamental in the tone of a reed pipe. A narrow opening, on the other hand, allows the upper partials to be emphasized.
In addition to its shape, the surface of the face of a shallot has an effect on
the
timbre of a reed. If the brass face around the opening in a shallot is merely
burnished or polished,
the tongue strikes against another piece of metal, and a bright sound is produced.
If, however,
the face of the shallot is covered with leather, as is sometimes done, the tone will
be darker, or
even dull by comparison with an uncovered shallot.
Similarly, tongues can vary in the details of their construction, and different timbres can be produced from a single pipe if different tongues are substituted. The major points of variation in reed tongue construction are:
In flue pipes, it is possible to look at the body, estimate its length, and make a general determination of the pitch the pipe will sound. The general rule that longer pipes make lower sounds applies to flue pipes as well as to piccolos and tubas in the orchestra. In the case of reeds, however, this is not possible, because, as pointed out above, the basic pitch is determined by the tongue, not by the resonator. As described in the following list, the length of a reed resonator may in fact be an indicator of timbre, not pitch.
In general, when comparing the length of a reed resonator to the length of the body of an open flue pipe of the same pitch - - the organ standard, 18 the possible relationships fall into three categories. The reed resonator may be
As pointed out in the list above, the length of the resonator may change through the range of a rank of reeds for a variety of reasons. An example of such a change can be seen in the two Krummhorn pipes shown in the photograph to the right. 48 If this were a picture of two flue pipes, the assumption that the shorter pipe sounds a higher note would be correct. In this case however, the shorter pipe actually sounds a note lower (b) than the longer pipe (c').
The pipes are from a rank that is located in a short case. The c' pipe
has a full-length resonator, but the resonator of the b is only half length.
All pipes
of that octave have half-length resonators so that they can fit within the limits
imposed by
the small space. Although other options, including mitering the resonators, might
have been
chosen, the pipe maker elected to keep the resonators of the lower two octaves
shorter by making
them of fractional length. This change in length affects the timbre but not the
pitch of the pipes.
The photograph at the left gives a closer look at the blocks, shallots and tongues of the same two pipes. They are much closer in size than the two resonators. Careful measurement shows that the tongue on the right is actually shorter in its free length (below the wire) than that on the left. It therefore produces a higher pitch. The principle demonstrated by these two pipes is generally true: a change in resonator length through the range of a rank of reeds does not indicate the same change in pitch that a similar change in body length does in a rank of flue pipes. A change in tone color takes place instead, unless some compensations are made in other parts of the pipe.
The primary function of a reed resonator is to modify the timbre of the tone produced by the vibrating tongue. It is the shape of the resonator that can be altered to suppress or emphasize certain elements of the overtone series in order to achieve the desired sound.
Unlike the situation found in flue pipes, a completely closed resonator is not possible. In a closed flue pipe, the air that enters the mouth can exit through the mouth, but there is no similar opening at the base of a reed resonator. Therefore, resonators must contain an opening at some point through which the air that enters the resonator through the shallot and block can exit, and all reed resonators are either open or partially closed. There are two basic shapes for reed resonators, either of which may be open or partially closed.
Conical Resonators.
The resonator in the photograph to the right is in the shape of an inverted cone, one of the most common shapes found in reed pipes. 49 It is open at the wider end, and has a small opening about one fifth of the way down from the top. The opening in the side allows some further modification to the tone as well as some leeway in tuning. It is commonly called a voicing curl. Resonators of this shape allow the full development of overtones in the sound created by the tongue, and are also found in reeds such as Trumpets, Oboes and Tubas.
The degree to which the
cone enlarges as it extends from the block has an effect on tone color, in that a
broader conical
shape will emphasize the fundamental more than a narrow one. The conical resonator
depicted
above is from a Posaune, a large, full-bodied reed often found in pedal divisions.
The picture to
the right is of a Fagotto resonator.
50 The tone of this pipe is rich in
overtones, with very little
fundamental present.
Cylindrical Resonators.
The other primary shape for a resonator is cylindrical, as seen in the photograph to the right. The pipe is a Dulzian, one of the reed timbres in a family of sounds that includes Krummhorns (Cromornes), Clarinets, Vox Humanas and several other stops generally called "regals." This resonator is partially closed, and the movable cap at the top of the resonator allows the same fine tuning of both pitch and timbre that the voicing curl does in the conical resonators above.
Other Resonator Shapes. Because of the great variety found in reed timbre, there is a parallel variety to be seen in the shapes of reed resonators, but most of them derive from the two basic shapes shown above. Some of that variety can be seen in the photograph below, which shows a number of reed resonators in a voicers workshop. 51 The tallest resonator is from a rank meant to be mounted as an en chamade Trumpet. Others include several Oboes and Trumpets, an English Horn, an Apfelregal, and a reed-voicers joke in the form of a resonator made of two paper cups.
© 1998, James H. Cook