MODULATION. - This term substantially indicates the passage from one key to another.
The means by which such a passage can be effected are extremely varied and different in individual cases, by reason of the number of chords employed, of the character one wishes to give to the modulation, of its duration and complexity, of its style and its expressive value: and more technically, by reason of the dissonances that contribute to it, of the greater or lesser prevalence of diatonicism or chromaticism, of the different procedures by which the notes of the destination key are introduced, successively or simultaneously, gradually or suddenly canceling those of the starting key, with or without the use of suspensions, of symmetrical designs, of rhythmic and melodic elaborations. Accordingly, it is customary to distinguish modulations, according to their duration, into momentary, provisional, definitive. Momentary ones abandon the destination key immediately after having reached it; provisional ones remain there for a more or less extended time without eliminating the need for the return to the principal key; definitive ones replace the principal key with another principal key. Modulations can be immediate (transitions); but the concept is tenable that true modulation is always mediated, and consists in finding one or more links of connection between two keys. As for the relationship of keys, modulations are distinguished into close and distant. Close keys are those having at the signature one accidental more or less than the key taken as the basis. One can modulate to a close key by momentarily touching distant keys. Thus a further distinction is made between direct and indirect modulations. For example: from C major to A-flat major through F minor: direct modulation; from C major to A-flat major through E major, G minor and E-flat major: indirect modulation, that is, to a close key through distant keys. In the great authors modulation is never an end in itself, but always has an intimate relationship with the structure of the piece, or a particular expressive, descriptive, allusive character, justified by the words in the case of music set to a given text. In the obbligato recitatives of the great nineteenth-century Italians, examples often occur of modulations adhering, with the happiest effect, to the motions of the soul of a given character; in the masters of the lied, the art of modulating according to the suggestions of the poetic text is exquisite and most refined. In symphonic music there are modulations necessary to the very construction of the piece, that is, modulations required by the musical form that carries within itself its own tonal laws. Thus, for example, the first movement of a sonata, or of a quartet, is set upon two principal symphonic ideas, of which the second presents itself in the key of the major dominant or of the so-called relative major (and sometimes in other keys, subordinate to the principal one). The evolution of musical language in the last fifty years has enormously enriched the technique of modulation both in the polytonal field (simultaneous modulations) and in the modal one (unimodal, intermodal, polymodal modulation).
Edgardo Carducci-Agustini