DOUBLE Employment, in Music, a name given by M. Rameau to the two different manners in which the chord of the sub-dominant may be regarded and treated, viz. as the fundamental chord of the sixth superadded, or as the chord of the great sixth, inverted from a fundamental chord of the seventh. In reality, the chords carry exactly the same notes, are figured in the same manner, are employed upon the same chord of the tone, in such a manner, that frequently we cannot discern which of the two chords the author employs, but by the assistance of the subsequent chord, which resolves it, and which is different in these different cases.

To make this distinction, we must consider the diatonic progress of the two notes which form the fifth and the sixth, and which, constituting between them the interval of a second, must one or the other constitute the dissonance of the chord. Now this progress is determined by the motion of the bass. Of these two notes, then, if the superior be the dissonance, it will rise by one gradation into the subsequent chord, the lower note will keep its place, and the higher note will be a superadded sixth. If the lower be the dissonance, it will descend into the subsequent chord, the higher will remain in its place, and the chord will be that of the great sixth. See the two cases of the double employment in Rouffleau's Musical Dictionary, Plate D, fig. 12.

With respect to the composer, the use which he may make of the double employment, is to consider the chord in its different points of view, that from thence he may know how to make his entrance to it, and his exit from it; so that having arrived, for instance, at the chord of the superadded sixth, he may resolve it as a chord of the great sixth, and reciprocally.

M. D'Alembert has shown, that one of the chief uses of the double employment is, that we be able to carry the diatonic succession of the gamut even to an octave, without changing the mode, at least whilst we rise; for in descending we must change it. Of this gamut and its fundamental bass, an example will be found in Rouffleau's Musical Dictionary, Plate D, fig. 13. It is evident, according to the system of M. Rameau, that all the harmonic successions which result from it, are in the same tone: for, in strictness, no other chords are there employed but three, that of the tonic, that of the dominant, and that of the sub-dominant: as this last, in the double employment, constitutes the seventh from the second note, which is employed upon the sixth.

With respect to what M. D'Alembert adds in his Elements of Music, p. 70, and which he repeats in the Encyclopédie, article Double emploi, viz. that the chord of the seventh re fa la ut, though we should even regard it only as inversion of fa, la, ut, re, cannot be followed by the chord ut mi sol ut; "I cannot (says Rousseau) be of his opinion in this point.

"The proof which he gives for it is, that the dissonance ut of the first cannot be resolved in the second; and this is true, since it remains in its place; but in this chord of the seventh re fa la ut, inverted from this chord of the superadded sixth, fa la ut re, it is not the ut, but the re, which is the dissonance; which, of consequence, ought to be resolved in ascending upon mi, as it really does in the subsequent chord; so that this procedure in the bass itself is forced, which, from re, cannot without an error return to ut, but ought to ascend to mi, in order to resolve the dissonance." " M. D'Alembert afterwards shows, that this chord re fa la ut, when preceded and followed by that of the tonic, cannot be authorized by the double employment, and this is likewise very true; because this chord, though figured with a 7, is not treated as a chord of the seventh, neither when we make our entrance to it, nor our exit from it; or at least that it is not necessary to treat it as such, but simply as an inversion of the superadded sixth, of which the dissonance is the bafs: in which case we ought by no means to forget, that this dissonance is never prepared. Thus, though in such a transition the double employment is not in question, though the chord of the seventh be no more than apparent, and impossible to be resolved by the rules, this does not hinder the transition from being proper and regular, as I have just proved to theorists. I shall immediately prove to practical artists, by an instance of this transition: which certainly will not be condemned by any one of them, nor justified by any other fundamental bafs except my own. (See the Musical Dictionary, Plate D, fig. 14.)

"I acknowledge, that this inversion of the chord of the sixth superadded, which transfers the dissonance to the bafs, has been censured by M. Rameau. This author, taking for a fundamental chord the chord of the seventh, which results from it, rather chose to make the fundamental bafs descend diatonically, and resolve one seventh by another, than to unfold this seventh by an inversion. I had dissipated this error, and many others, in some papers which long ago had passed into the hands of M. D'Alembert, when he was composing his Elements of Music; so that it is not his sentiment which I attack, but my own opinion which I defend."

For what remains, the double employment cannot be used with too much reserve, and the greatest masters are the most temperate in putting it in practice.

DOUBLE Fichy, or Fiché, in Heraldry, the denomination of a crois, when the extremity has two points; in contradistinction to fiché, where the extremity is sharpened away to one point.

DOUBLE Octave, in Music, an interval composed of fifteen notes in diatonic progression; and which, for that reason, is called a fifteenth. "It is (says Rousseau) an interval composed of two octaves, called by the Greeks disdiapason."

It deserves, however, to be remarked, that in intervals less distant and compounded, as in the third, the fifth, the simple octave, &c. the lowest and highest extremes are included in the number from whence the interval takes its name. But, in the double octave, when termed a fifteenth, the simple number of which it is composed gives the name. This is by no means analogical, and may occasion some confusion. We should rather choose, therefore, to run any hazard which might occur from uniformly including all the terms of which the component intervals consist, and call the double octave a fifteenth, according to the general analogy. See INTERVAL.