Quartal & Quintal harmonies are used in musical compositions where the composer has a particular preference for fourth & fifth intervals. With quartal harmonies, these can be seen in perfect fourth, augmented fourth and diminished fourth intervals. Likewise, quintal harmonies perfect fifth, augmented fifth and diminished fifth intervals.
Historically used in pieces of dramatic classical music to convey a sense of chaos and dissonance, and later in Jazz as a form of tonal colouring. These principles evolved to lend themselves to those experimenting in progressive rock music in the later half of the 20th century. Examples can be found in the songs "Tarkus" by Emerson, Lake & Palmer and "Zoot Allures" by Frank Zappa. Much of the work by Robert Fripp of King Crimson makes great use of these harmonies which are easily accommodated on the guitar with the use of his New Standard Tuning.