In Western music and music theory, augmentation (from Late Latin augmentare, to increase) is the lengthening of a note or the widening of an interval.

Augmentation is a compositional device where a melody, theme or motif is presented in longer note-values than were previously used. Augmentation is also the term for the proportional lengthening of the value of individual note-shapes in older notation by coloration, by use of a sign of proportion, or by a notational symbol such as the modern dot. A major or perfect interval that is widened by a chromatic semitone is an augmented interval, and the process may be called augmentation.

Augmentation in composition

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.

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:thumb|Debussy, "Dr Gradus" from Children's Corner, bars 1-3thumb|center|500px|Debussy, "Dr Gradus" from Children's Corner, bars 1–3

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:thumb|Debussy, "Dr Gradus" from Children's Corner, bars 36-43thumb|center|500px|Debussy, "Dr Gradus" from Children's Corner, bars 36–43

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.”

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  • Prelude in E minor, Op. 28, No. 4 at The Mutopia Project.