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,
Seventh octave but some people who are capable of singing in the bass range (like singers Adam Lopez or Nicola Sedda) can do it. While notes in the sixth octave, between soprano high C and C7, can have enough color to sound flutey or canary-like, the squeaky, whistly tones in the seventh octave help give the whistle register its name, as do the piercing qualities of notes in this octave. Seventh octave The seventh octave is the highest octave of a piano. Using middle C (C4) as a guide, the next higher C is C5 or tenor C. The next C is