Augmented seventh Augmented seventh In classical music from Western culture, an augmented seventh is an interval produced by widening a major seventh by a chromatic semitone. For instance, the interval from C to B is a major seventh, eleven semitones wide, and both the intervals from C to B, and from C to B are augmented sevenths, spanning twelve semitones. Being augmented, it is classified as a dissonant interval. However, it is enharmonically equivalent to the perfect octave. Since an octave can be described as a major seventh augmented by a diatonic semitone, the augmented seventh is the sum of an octave,
Octave the assumption that pitches one or more octaves apart are musically equivalent in many ways, leading to the convention "that scales are uniquely defined by specifying the intervals within an octave". The conceptualization of pitch as having two dimensions, pitch height (absolute frequency) and pitch class (relative position within the octave), inherently include octave circularity. Thus all Cs, or all 1s (if C = 0), in any octave are part of the same pitch class. Octave equivalency is a part of most "advanced musical cultures", but is far from universal in "primitive" and early music. The languages in which the