(1) A term used in the context of improvised embellishment during the Renaissance and Baroque periods to describe a melodic figure that replaces a long note with notes of shorter value. Diminution is close in meaning to the English ‘division’, the Italian passaggio, the Spanish glosa, and the French double. Whereas specific graces such as trills or appoggiaturas were applied to single notes, diminutions served to decorate the transition from one note of a melody to the next with passage-work, giving scope for virtuoso display. 16th- and 17th-century instruction books provide tables of diminution formulae for the most used musical intervals, in various note values, which performers could learn by rote and apply to any piece of music. Written-out examples in musical works by leading performers of the time show that in practice diminutions were most often combined with specific graces to decorate the repeat of a phrase or section of a work, or verses of a strophic song after the first, giving the effect of a musical variation. By extension, a melody so embellished was sometimes called a ‘diminution’. In the 17th century, diminution techniques were employed with particular sophistication in the French air de cour, air and air sérieux, and in the English Division upon a ground. While by the end of the Baroque period French and German composers were notating much of the ornamentation they considered appropriate in their music, extempore diminutions were still required for a stylish interpretation of music in the Italian style, especially the slow movements of the sonata and concerto, and the repeat of the A section in the performance of da capo arias. See also Improvisation, II, 1 and 2; Ornaments; Variations; and Viola bastarda.
(2) The statement of a theme or melodic fragment in note values that are shorter (usually uniformly so) than those originally associated with it. Diminution is found in mensural notation, notably in isorhythmic motets and cantus firmus masses, and again in baroque and subsequent contrapuntal and especially canonic or fugal techniques (see Fugue). In Proportional notation a range of signs is available for the purpose of reducing the value of note shapes in a variety of mathematical ratios. Diminution is the opposite of Augmentation.
See also Diminished interval.
GREER GARDEN (1), ROBERT DONINGTON/R (2)