Augmented seventh Adding a diesis to this makes up an octave. Hence, this interval's complement, the diminished second, is often referred to as a diesis. 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
Octave standard 88-key piano keyboard, while the C an octave higher is C. The notation "8" or "8" is sometimes seen in sheet music, meaning "play this an octave higher than written" ("all' ottava": "at the octave" or "all' 8"). "8" or "8" stands for "ottava", the Italian word for octave (or "eighth"); the octave above may be specified as "ottava alta" or "ottava sopra"). Sometimes "8" is used to tell the musician to play a passage an octave "lower" (when placed under rather than over the staff), though the similar notation "8" ("ottava bassa" or "ottava sotto") is also used.