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
Short octave "C/E", meaning that the lowest note is a C, played on a key that normally would sound E. A second type of short octave used the keys to play the G major scale Here, the exotic bass notes C and D are sacrificed to obtain the more essential A and B. The notation for the pitch range of such an instrument is "G/B". The following diagram illustrates this kind of short octave: In stringed instruments like the harpsichord, the short octave system created a defect: the strings which were tuned to mismatch their keyboard notes were in general too short