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,
Octave (liturgy) Epistle and Gospel of the Feast are repeated again at the Divine Liturgy. The term "octave" is applied to some church observances that are not strictly liturgical. For example, many churches observe an annual "Octave of Prayer for Christian Unity", which runs from 18 January to 25 January. The octave was established in 1895 by Pope Leo XIII for the period between Ascension and Pentecost. In 1909, Pope Pius X approved the transfer of this octave to the period between the former feast of the Chair of St. Peter and the feast of the Conversion of St. Paul. In 1968,