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Scan 139
A dictionary of musical terms, 1889
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1and their present position in music. These authors (see Coussemaker, p. 49) classify the unison and octave as perfect consonances; the 4th and 5th as middle consonances; the major and minor third as imperfect consonances.
3The next important step in the progress of harmony seems to have been the giving due consideration to what we now term the relative motion of the parts. In the early examples (1 to 3) it must have been observed that there is nothing but similar motion; in Ex. 4, oblique motion is mixed with similar; and next we find authors boldly laying down the law that when the principal (or melody) ascends, the added organum should descend, and vice versa (ubi in recta modulatione est elevatio, ibi in organica fiat depositio et e converso). This acknowledgment of the beauty and value of contrary motion must have given a new impulse to the art. Thus step by step did it grope its way, till in the 11th century important treatises on it were produced, and there can be also traced that sure sign of a healthy circulation of thought, a marked partisanship of different and opposed systems. After this period, instead of the "principal" and its "organum," we begin to read of a "tenor" and its "descant," and by almost imperceptible degrees the old system dies away as the new is grafted and feeds on it. It must not, however, be supposed that the successive changes in diaphony, above sketched, occurred in the exact order in which they are presented to the reader. Systems of art are never of sudden growth, they overlap each other; they perhaps grow side by side for years, perhaps for centuries, until those which have in them the smallest power of development decay, and leave the less-matured but better-constituted systems to survive, with fresh opportunities of thriving.
5Descant, Discantus (Lat.), may be said to have come into existence at the end of the 11th or beginning of the 12th century. The word itself is thought by some to be merely a latinized synonym of diaphony; others, among them Franco, considered it to be connected with de cantu, something framed on or growing out of a melody. Originally, as had been previously the case with diaphony, it consisted of two parts only, but later in its life developed into motetts and various other forms of composition. The real difference between diaphony and descant seems to have been that the former was rarely, if ever, more complicated than note against note, whereas descant made use of the various proportionate value of notes—"Discantus est aliquorum diversorum cantuum consonantia, in quo illi diversi cantus per voces longas, breves, vel semibreves proportionaliter adæquantur, et in scripto per debitas figuras proportionari ad invicem designantur" (Johan. de Moravia). It also included notes altered semitonally by accidentals, under which circumstances it was called musica ficta vel falsa, feigned or false music. This fact adds interest to a discussion which took place between M. Fetis and M. Coussemaker. The former taxed the latter with having misinterpreted his published specimens of diaphony, because, in it were introduced the tritone and the lesser 5th. M. Coussemaker's answer seems conclusive—it is to the effect that if the parallel motion of diaphony were consistently preserved, either such intervals must occur, or accidentally altered notes, outside the scale, must have been introduced; and such has not been proved to have taken place.
7The rules of descant are numerous, and they provided for the regular addition of one part to any other part according to the movement of the tenor. The particular interval by which the tenor proceeded, dictated to the descant its own progression. It would be useless to give the rules here, as they can only be mastered by the student who carefully reads the many treatises on the subject, so elegantly reprinted by the indefatigable M. Coussemaker (Script. de Musica Medii Ævi). The scope of these rules was from time to time expanded, and in a treatise of the 14th century by Theinred, reprinted by W. Chappell (in the "Choir" newspaper of April 9, 1870), the divergences of the later from the earlier systems are apparent.
9At this time, or even earlier, such expressions as cantus firmus and contrapunctus begin from time to time to be used, giving the first intimation of the art of adding counterpoint to a canto fermo, which was soon to supersede descant, as descant had superseded diaphony.
11Opinions have been divided as to whether descant was merely a form of regulated improvisation, or whether it was a written art. In all probability, it grew from one state into the other. At first, without doubt, its rules were intended to direct a musician how to add "contrappunto alla mente;" afterwards, when an interesting and successful descant had been framed, and perhaps often repeated, it would indeed be strange if the author had made no attempt to lengthen its existence by committing it to paper; indeed, one sentence from Johannes de Muris substantiates the fact beyond dispute. He says, "Nihil enim prohibet in duobus cantibus simul esse cantantes plures, tam in tenore quam in discantu." It is inconceivable that a number of voices could be found to add descants impromptu without serious discrepancies. Descants were sometimes sung without words.
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