Organ

In reedwork the French horn is, roughly speaking, the equivalent of the flute, the trumpet of the diapason, the English horn (cor anglais) of the viol species. The clarinet corresponds with a gedeckts and has resonators of only half length, just as the har monic reeds have resonators of double length. For the resonators of reeds are of about the same length on the bodies of flue-pipes giving the same pitch of note and in these two cases at least, they depart similarly from the normal. But at all times the reed stops are much less numerous than the flue, and although often blown by a wind of much heavier pressure do not compete with them on their own ground.

Pitches of Stops.

Organ stops which speak at the pitch indi cated by the written notes are called 8ft. or "unison stops" because an open flue-pipe about so long would be needed to sound CC, the lowest note of the manual clavier. By analogy reeds and even gedeckts are 8ft. stops, if they sound at 8ft. or "unison" pitch throughout. So, too, the i6ft. stops are those which sound an octave below the "unison" pitch of the manuals. A gedeckt with a body 8ft. long would still be a i6ft. stop, because of its i6ft. pitch. Stops as grave as of 32ft. pitch appear on the pedal and in very large organs on the manuals, their name signifying a pitch two octaves below that of the manuals.

Of stops which sound higher than the 8ft. pitch of the keys the 4ft. stops give the octave, 2ift. stops the twelfth, 2ft. stops the fifteenth or super-octave, i s f t. stops the seventeenth or tierce, stops the nineteenth or larigot, stops the flat twenty first or septieme, 'ft. stops the twenty-second, and so (in theory at least) ad infinitum, the interval between the ranks becoming smaller as the ranks themselves are of acuter pitch, in accordance with the natural law of what is known as the harmonic series. Practical considerations, however, must always set arbitrary limits, and in this case they rule : (I) ranks above the fifteenth are too small and acute to be carried through the whole compass of the keyboard in an unbroken form; (2) no rank more dissonant than a minor seventh—or at most a major second—is tolerable any where in the tonal economy of the organ; (3) for most ordinary purposes ranks sounding octaves, thirds and fifths sufficiently represent the harmonic series. As a matter of practice all stops above the fifteenth form a part of what are called the mixtures, and except for special purposes (see later under Choir Organ, where the purpose of independent mutations is discussed) are employed collectively as "upperwork." Manual stops of i6ft., 8ft. and 4ft. pitches, being the most consonant with the unison or standard, are termed "foundation work" (Fr. fonds) ; and thus, in the upper work and in the foundation work respectively, the two complementary ideas of brilliance and gravity are fulfilled.

The twelfth and fifteenth are sometimes independent ranks, some times part of the mixtures. As a rule, flute and viol stops are con fined to the foundation pitches—reeds always. But diapasons being of a tone peculiar to the organ represent upperwork as well as foundation.

And now to consider the stops as grouped in the various sec tional organs and the sections themselves as related to the organ at large, premising that letters attached to stop-names in this article indicate their genus, species or tone-quality, i.e., d--=-- diapason, f = flute, v= viol, g = gedeckt, r = reed, echo = lesser toned.

Great Organ.

The Great Organ (Fr. Grand Orgue; Ger, Hauptwerk) as its name implies is the most important of these, and forms the tonal backbone of the whole instrument.

In English and American organs it is chiefly conspicuous for a diapason quality which pervades it throughout. Especially typi cal is the open diapason 8ft. without which scarcely an organ was ever built. To supply the requisite foundation for a large Great Organ there may be as many as three or four open diapasons, though they would not all be similarly scaled and voiced. If the first diapason is a powerful stop of full and round quality, the sec ond is almost sure to be of a lighter and sharper tone; and some times in the interests of variety a geigen (dv) or gemshorn (dg) is substituted for the third or fourth.

The double open diapason, i6ft. octave or principal 4ft., twelfth 23ft., fifteenth 2ft., and mixtures are equally germane to the Great Organ, and may be likened to the roots, branches and twigs of the diapason trunk.

On the other hand the substratum of the French Great Organ is not so much a diapason as a flute one ; for flutes are regarded as a kind of neutral canvas on which other and more positive tone col ours (especially diapasons) can be laid and mixed. Again, Spanish Great Organs have no open diapasons as understood by English speaking musicians; instead they have a foundation of hybrid flute-viol kind which is said to be particularly disagreeable. Nor does the average German Great Organ appeal to our ears much more, since its pipes are too often made of thin metal, and as a consequence sound hard and brassy. The gedeckts, e.g., bourdon i6ft., stopped diapason 8ft., flute couverte 4ft., add considerable body to the diapasons besides having their own special value. In the United States a Doppelflote (gedeckt with two mouths) is very popular. Where neither money nor space can be found for the pipes of actual i6ft. length, a bourdon i6ft. (g) frequently takes the place of a double open diapason.