Seventh chord an augmented fifth, and an augmented seventh (i.e., a sequence of 3 major thirds, such as C–E–G–B), is a rarely used tertian seventh chord. The reason is that the augmented seventh interval is enharmonically equivalent to one entire octave (in equal temperament, 3 major thirds = 12 semitones = 1 octave) and is hence perfectly consonant with the chord root. The seven commonly used chords are: Seventh chords can also be constructed using augmented or diminished thirds. These chords are not tertian and can be used in non-tertian harmony. There are many (mathematically, 64) chords that can be built, however,
Short octave composer Peter Philips wrote a pavane in which the left hand plays many parallel tenths. This is a considerable stretch for many players, and become even harder when (as in Philips's pavane), there sometimes other notes included in the chord. Of this piece harpsichord scholar Edward Kottick writes, "The sensuality of effortlessly achieving tenths is so strong, so delightful, that one cannot really claim to know the piece unless it has been played on a short-octave keyboard." A later composer who wrote music conveniently playable only on a broken-octave instrument was Joseph Haydn, whose early work for keyboard was intended