Tritone

The interval of three whole tones (the augmented fourth=diminished fifth). It is an awkward interval in vocal music. In the Lydian mode starting on F, the interval of F to B is an augmented fourth. It naturally occurs between the fourth and seventh degrees of major and descending melodic minor scales. In counterpoint, it is a very dissonant interval associated with depiction of anguish. The crampy nature of a diminished triad is relieved by using them in first inversion (iib and viib in minor mode).