Dictionary of Music - Birding America

organ 289this family of pipes, among them open diapason(principal), flautino, and violin diapason; flute, agroup of pipes, some stopped (stopped flute) andothers open (chimney flute, spindle flute, blockflute) which resemble the sound of a flute in thatthey sound few overtones; string, a group of pipeswhose tone resembles that of various stringed instrumentsand whose members have such names ascello, viola, and gamba (for viola da gamba, the oldbass viol). Flue stops that combine elements of severalcategories are called hybrid stops. Among themare gemshorn, combining string and flute, andspitzflute, combining principal and flute.There are two main kinds of reed pipe, chorusand solo. The chorus reeds are named for trumpetsand other brasses (trombone, trumpet, posaune, clarion)but their tone color differs considerably fromthese instruments; they are usually made in fourfoot,eight-foot, and sixteen-foot sizes and are usedtogether with the full organ. The solo reeds resemblethe tone of various woodwinds, for which they arenamed; among them are the bassoon, English horn,clarinet, and oboe.The organ has an immense range, about nineoctaves in all, which is larger than that of any othernonelectronic instrument. The written range isshown in the accompanying example, but this rangeis greatly exceeded through the use of two-foot andsixteen-foot stops (see below). To have the organ’srange, a piano would need a keyboard nearly halfagain as large. The organ manual actually containsonly five octaves. However, the organ has not onlypipes of normal pitch, which sound the note playedfig. 172 p/u from p. 300on the keyboard, but additional pipes whose pitch isone and two octaves higher or lower. The normalpitch, called unison, is indicated by the sign 8′ (or 8-foot), the pitch one octave lower is indicated by 16′,and the pitches one, two, and three octaves higherare indicated by, respectively, 4′, 2′, and 1′. On thepedalboard the normal pitch is 16′ (an octave belowthe manual’s), and the pitch one octave lower is 32′.These pipes are brought into play by the variousstops and couplers.The stops, too, are described in terms of size, as4′, 8′, and so on. An 8′ stop sounds the pitch exactlyas written, a 4′ stop sounds an octave higher, a 16′stop an octave lower, and so on. The stops are namedfor the kinds of pipe they control, that is, principalstop, chorus stop, and so on. Thus an “8′ principalstop” controls all the flue pipes of the type known asprincipal and sounding the same pitches as written.A 4′ principal would control the same kinds of pipebut an octave higher in pitch. These stops are knownas foundation stops.In addition, there are two special kinds of stop,mutation stops and mixture stops. A MUTATION STOPmakes available not the unison pitch but one of itsharmonics (overtones). The most important mutationstops are quint stops and tierce stops. Quintstops sound the twelfth, the third note in the harmonicseries; for example, if middle C is played, theG in the octave above middle C (a twelfth higherthan middle C) will sound. Tierce stops sound theseventeenth, the fifth note in the harmonic series; forexample, if middle C is played, the third E abovemiddle C will sound (two octaves and a thirdhigher). Mutation stops are not played alone, but incombination with other notes, whose tone color theychange by reinforcing a particular harmonic.A MIXTURE STOP, also called compound stop,brings into play more than one pipe per note, that is,a chord. Usually combining anywhere from two toseven pipes per note, drawn from both unison andmutation ranks, the mixture stop is used togetherwith a strong unison stop to vary, enrich, or reinforcethe tone color. Among mixture stops are thecymbal, fourniture, plein jeu, and Scharf.The stops selected for an organ by the builder arecalled its specification; the stops selected by theorganist in playing are called the registration.Though some stops are naturally soft and othersloud, their tone color influencing their volume, theorganist also can control volume by means of a specialpedal, the swell pedal. Located just above thepedalboard, the swell pedal controls a set of shuttersin front of the pipes of one or more manuals, whichare enclosed in a box; pressing it down gradually