Augmentation (music)

A melody or series of notes is augmented if the lengths of the notes are prolonged; augmentation is thus the opposite of diminution, where note values are shortened. A melody originally consisting of four quavers (eighth notes) for example, is augmented if it later appears with four crotchets (quarter notes) instead. This technique is often used in contrapuntal music, as in the "canon by augmentation" ("per augmentationem"), in which the notes in the following voice or voices are longer than those in the leading voice, usually twice the original length. The music of Johann Sebastian Bach provides examples of this application:

Other ratios of augmentation, such as 1:3 (tripled note values) and 1:4 (quadrupled note values), are also possible. A motif is also augmented through expanding its duration.

Augmentation may also be found in later, non-contrapuntal pieces, such as the Pastoral Symphony (Symphony No. 6) of Beethoven, where the melodic figure first heard in the second violins at the start of the "Storm" movement ("Die Sturm"):

is heard again in an augmented and transposed version in the same movement’s closing ten bars:

Examples of augmentation may be found in the development sections of sonata form movements, particularly in the symphonies of Brahms and Bruckner and in the protean leitmotifs in Wagner’s operas, which undergo all kinds of transformation as the characters change and develop through the unfolding drama. "Leitmotifs accumulate meaning, through expanding and fulfilling their musical potential."

In “Doctor Gradus ad Parnassum”, the first movement of his Children’s Corner Suite, Debussy exploits augmentation in a humorous vein. It opens with a vigorous parody of a technical study by a pedagogical composer such as Clementi, involving a seemingly perpetual stream of fast semiquavers:

In bar 33, this energetic movement subsides, leading to a dreamy passage in the key of D flat, where the opening figures of the piece move at half speed:

According to Frank Dawes, in this piece “An amusing picture of a child practising is conjured up, beginning with the best of intentions, growing weary and plainly yawning with boredom in the D flat section.” Listen.

An augmented interval is an interval obtained from a major interval or perfect interval by widening it by a chromatic semitone, meaning that the interval is widened by a semitone, but the staff positions are not changed (only an accidental is changed). For example, an augmented third is a chromatic semitone wider than the major third: starting with the interval from A♭ to C, which is a major third, four semitones wide, the interval from A♭ to C♯ is an augmented third, spanning five semitones, but the same staff lines. By contrast, the interval from A♭ to D♭ is not an augmented third (it is a perfect fourth): even though it is four semitones wide, it spans four staff positions, and is thus a fourth, not a third; it is a diatonic semitone wider than a major third. The augmented fourth (A4) is the only augmented interval that appears in diatonic scales (in D♭ major it occurs between G♭ and C). The standard abbreviations for augmented intervals are AX, such that an augmented third = A3.

A good example of this can be seen in the left hand part of Chopin's famous E minor prelude Op. 28, No. 4. Many of the chord sequences change with the top or bottom note augmenting or diminishing the next chord as the music progresses.

An augmented chord is one which contains an augmented interval, almost invariably the 5th of the chord. An augmented triad is a major triad whose fifth has been raised by a chromatic semitone; it is the principal harmony of the whole tone scale. For example, the D♭ augmented triad contains the notes D♭, F, A.