Augmented

What it means

An interval is called augmented when it is extended by a semitone relative to its perfect or major form — without the degree count changing. The perfect fourth becomes the augmented fourth, the major second the augmented second, the perfect fifth the augmented fifth. All augmented intervals are dissonant.

In the notation

The extension is recognizable only from the accidentals, for the degree count stays the same: C–F is a fourth, C–F-sharp likewise, only an augmented one. Precisely herein lies the point of the spelling — it fixes which degrees are meant and where the notes go on. An augmented fourth strives apart, while a sonically identical diminished fifth draws together.

Musical use

Augmented intervals arise through alteration and correspondingly carry tension. The augmented second forms in harmonic minor between the sixth and seventh degrees; the melodic form of the minor scale smooths it out, because it was felt to be melodically awkward. The augmented fifth belongs to the augmented triad, which divides the octave evenly and therefore has no unambiguous root. The augmented sixth carries the augmented sixth chord, a tense turn of phrase before the dominant.

In inversion, an augmented interval becomes a diminished one: the augmented fourth becomes the diminished fifth, the augmented second the diminished seventh.

An interval becomes augmented through raising the upper note or lowering the lower note by a chromatic semitone. From perfect and major intervals, augmented ones thus arise, for instance the augmented fourth or the augmented second. Sonically, augmented intervals can coincide with others, the augmented second for instance with the minor third; their spelling, however, reveals their pull, for augmented intervals want to widen outward.

Performance practice

With flexible intonation, take the upper note rather high and the lower rather low, so that the tension becomes audible. And do not let the sound deceive you — check the spelling; it tells you where the voice is going.