MODULATION, in Music, is a changing of the key, or mode, during the progress of a composition. The word is derived from the Latin verb modulor, to compose or sing in measure, melody of. some sort being inferred.
Though it is not quite clear what the ancients meant by the term modnlatio, yet the presumption is that they signified by it the rise and fall of the voice (accent us) and the measure of the syllables in recitation and declamation, altogether amounting to a kind of singing; and this we are inclined to think was the boundary, or nearly so, of their proficiency, and what they chiefly aimed at, in the vocal art.
In modern music, Modulation is a most important element, and in proportion to its importance should be the manner of treating it here ; but limited as we are in space, we anust be confined to some general remarks, illustratiug these by a few brief examples.
Modulation may be divided into Simple, Chromatic (or extraneous), and Enharmonic. Simple Modulation is a change from a given key to another nearly related to it, namely, its fifth, fourth, relative minor, or relative minor to its fifth ; and this modulation, not to be abrupt, is effected by at least one intermediate chord, which must belong to the harmony of the key into which it is intended to pass. Examples in four parts :— _ _ The close resemblance of the scales of a, v, A minor, and E minor, to the scale of e, renders the modulation easy and natural ; hence we have termed it simple. And it must now be observed, that the natural major key is here chosen as the diverging point merely on amount of its apparent simplicity; any other would have answered the purpose, provided the same relations had been preserved. Thus, for instance,
from the key of E e to its fifth B tz, is relatively the area as from c to G. Example Chromatic Modulation is the change from a given key to some other not analogous to it ; that is to say, to one differing much in scale, and, consequently, in signature. [Sloesrune.] Examples :— Enhermonie Modulation is the change from a given key to another quite unanalogous, by means of an enharmonic interval,—that is, by the same interval binominously considered ; as c and B:, AO and CI:, the. (Exuaunoxic.) Examples :— In these examples we have endeavoured to show the most direct method of modulating, and, except in one instance, by means of the dominant 7th and the diminished 7th, or their inversions. By the Intervention of a few additional chords, more elegant effects might have been produced, both as regards harmony and melody. But it must also be remarked that suddenness of transition is often essential to the design of the composer, in which case he takes the shortest road from key to key that the ear will permit.
It will be seen that we entirely differ from those who—perhaps misled by the word modulatio, and its interpretation by ancient writers—think that modulation may be carried on without any change of key. We are decidedly of opinion, though in opposition to some highly respectable authorities, that modulation and change of key are identical terms.