Tetrad (music)

In the music is meant by a four-note chord chord, in which four different tones sounding together.

The most common in classical music tetrachords are the seventh chords, which consist of three stacked thirds, ie triads add a seventh.

More commonly used four sounds caused by addition of the sixth, sixte ajoutée (added sixth ) called, or None which can also be interpreted as reduced by the Seventh Five sound according to the theory of Terzschichtung.