In music, quartal harmony is the building of harmonic structures with a distinct preference for the intervals of the perfect fourth, the augmented fourth and the diminished fourth. Quintal harmony is harmonic structure preferring the perfect fifth, the augmented fifth and harmony and theory a comprehensive source for all musicians pdf diminished fifth. Use of the terms quartal and quintal arises from a contrast, compositional or perceptual, with traditional tertian harmonic constructions.
In the Middle Ages, simultaneous notes a fourth apart were heard as a consonance. In the later 19th century, during the breakdown of tonality in classical music, all intervallic relationships were once again reassessed. Quartal harmony was developed in the early 20th century as a result of this breakdown and reevaluation of tonality.
Wagner’s opera Tristan und Isolde. This layering of fourths in this context has been seen as highly significant. Wagner’s use lasts much longer and resolves in a highly unorthodox manner for the time.
Wagner’s unusual chord is really a device to draw the listener into the musical-dramatic argument which the composer is presenting to us. However, fourths become important later in the opera, especially in the melodic development.