Augmented tredecime

The augmented thirteenth (A13) spans 22 semitones. It is the compound form of an augmented sixth and acts as a highly bright, tense upper extension.

Construction and spelling

A13 is built as an octave plus augmented sixth, for example C-A# above the octave. In equal temperament it may resemble m7 in another register context, but spelling indicates thirteenth-function expansion. This distinction is important in advanced voicing analysis.

Harmonic and melodic usage

Harmonically, A13 appears in altered dominant language, modern color chords, and dense upper-structure writing. Melodically, it yields expansive, intense leaps. It is used when maximum brightness and forward pull are needed.

Examples

• #13 color in altered dominant voicings
• Modern jazz/fusion sonorities with layered tensions
• Chromatic melodic writing with high extension focus

In practice

Practice A13 against A6 and m7 contexts to separate spelling-based function from pitch similarity. Test voicings carefully so #13 supports, rather than muddies, chord identity. This improves advanced extension control.