brightening up their tone, but should be shut off when the 4-feet principal is added, or when the to fifteenth is used, as the two tones do not amalgamate. The 16-feet stops on the manuals are intended to give weight and gravity of tone, and are always admirable with the full or nearly the full organ. In combination with the diapasons only their use is determined by circumstances; with a very full harmony they cause a muddy effect; with an extended harmony in pure parts they impart a desirable fullness and weight of tone, and seem to fill in the interstices of the unison stops: e.g.—
No. 1 would be injured by the addition of a 16-feet stop below the diapasons; No. 2 would improved by it.
The swell organ stops are very like the great organ in miniature, except that the reed-stops predominate more in tone, and are more often used either alone or with diapasons only, the stronger and more pronounced tone of the reeds being requisite to bring out the full effect of the crescendo on opening the swell box. The oboe alone, in passages of slow harmony, has a beautiful effect, rich yet distant. The choir organ is always partially composed of solo stops, and the bulk of its stops are usually designed for special effects when used separately, though with a certain capability of mixing in various combinations. It may be observed that qualities of tone which mix beautifully in unison will often not mix in different octaves. The union of one of the soft reedy-toned stops, of the gamba class, with an 8-feet clarabella flute, has a beautiful creamy effect in harmonised passages, but the addition of a 4-feet flute instead is unsatisfactory; and the combination with the clarabella, though so effective for harmony, would be characterless as a solo combination for a melody. The effect of a light 4-feet flute over a light 8-feet stop of not too marked character is often admirable for the accompanying harmonies to a melody played on another manual; Mendelssohn refers to this in the letter in which he speaks of his delight in playing the accompaniment in Bach's arrangement of the chorale 'Schmücke dich' in this way; the flute, he observes, 'continually floating above the chorale.' This class of effect is peculiar to the organ; it is quite distinct from that of doubling a part with the flute an octave higher in the orchestra; in the organ the whole harmony is doubled, but in so light and blending a manner that the hearer is not conscious of it as a doubling of the parts, but only as a bright and liquid effect.
In contrasting the stops on the different manuals, one manual may be arranged so as to be an echo or light repetition of the other, as when a selection of stops on the swell manual is used as the piano to the forte of a similar selection on the great manual; but more often the object is contrast of tone, especially when the two hands use two manuals simultaneously. In such case the stops must be selected, not only so as to stand out from each other in tone, but so that each class of passage may have the tone best fitted for its character. In this example, from Smart's Theme and Variations in A, for instance—
if the registering were reversed, the chords played on the flute-stop and the brilliant accompaniment on the swell reeds, it would not only be ineffective but æsthetically repugnant to the taste, from the sense of the misuse of tone: this of course would be an extreme example of misuse, merely instanced here as typical. The use of flute tone over reed tone on another keyboard is often beautiful in slow passages also; e. g. from [1]Rheinberger's Sonata in F♯:—
where the flute seems to glide like oil over the comparatively rough tones of the reed. Differing tones may sometimes be combined with good effect by coupling two manuals; swell reeds coupled to great-organ diapasons is a fine combination, unfortunately hackneyed by church organists, many of whom are so enamoured of it that they seldom let one hear the pure diapason tone, which it must always be remembered is the real organ tone, and the foundation of the whole instrument. Special expression may sometimes be obtained by special combinations of pitch. Slow harmonies played on 16-feet and 8-feet flutes, or flute-tuned stops, only, produce a very funereal and weird effect.[2] Brilliant scale passages and arpeggios, accompanying a harmony on another keyboard, may be given with an effect at once light and bizarre, with the 16-feet bourdon and the fifteenth three octaves above it. Saint-Saëns, in his first 'Rhapsodie,' writes
