Augmented seventh

The augmented seventh (A7) spans 12 semitones. It is a widened seventh and is enharmonically equivalent to the octave in equal temperament, but notation keeps seventh-function meaning.

Construction and spelling

A7 is formed by raising a major seventh by one semitone, for example C-B#. While it sounds like P8 in many contexts, the spelling indicates a seventh that expands upward. This distinction is theoretical and functional.

Harmonic and melodic usage

Harmonically, A7 is uncommon in basic repertoire but appears in advanced chromatic notation and enharmonic reinterpretation. Melodically, it can mark extreme leading-tone expansion. Its main use is precise notation in complex contexts.

Examples

• Chromatic spellings where B# resolves as a raised seventh
• Enharmonic reinterpretations in modulation analysis
• Theoretical comparisons between A7 and P8 function

In practice

Practice reading A7 as a spelled seventh, not just an octave sound. Compare C-B# with C-C to internalize function versus pitch equivalence. This improves advanced notation fluency.