ABSTRACT
The harmony draws its tones from major or minor scales to produce chords, vertical structures of three or more notes that sound together. Chords are identified by two symbols, a letter that represents its root, and another one that specifies the type of chord. The common qualities are major, minor, augmented, and diminished. The augmented triad consists of a major third on the bottom and a minor third on top. It is a volatile chord that seeks upward resolution. A tetrachord is a four-note chord, that corresponds to a combination of a whole-step, another whole-step and a half-step. Diabolus in Musica is the name given to the tritone, an interval of three whole steps, in the 17th century. Because it was considered dissonant, the use of the interval was prohibited by music theorists of the time.
