The modern Lydian mode is a seven-tone musical scale formed from a rising pattern of pitches comprising three whole tones, a semitone, two more whole tones, and a final semitone. Because of the importance of the major scale in modern music, the Lydian mode is often described as the scale that begins on the fourth scale degree of the major scale, or alternatively, as the major scale with the fourth scale degree raised half a step. This sequence of pitches roughly describes the scale underlying the fifth of the eight Gregorian (church) modes, known as Mode V or the authentic mode on F, theoretically using B but in practice more commonly featuring B. The use of the B as opposed to B would have made such piece in the modern day F major scale. Ancient Greek Lydian The name Lydian refers to the ancient kingdom of Lydia in Anatolia. In Greek music theory, there was a Lydian scale or "octave species" extending from parhypate hypaton to trite diezeugmenon, equivalent in the diatonic genus to the modern Ionian mode (the major scale). In the chromatic and enharmonic genera, the Lydian scale was equivalent to C D E F G A B C, and C C E F F A B C, respectively, where signifies raising the pitch by approximately a quarter tone. Medieval Lydian mode In the Middle Ages and Renaissance, this mode was described in two ways. The first way is the diatonic octave species from F up to F an octave above, divided at C to produce two segments: The second is as a mode with a final on F and an ambitus extending to F an octave higher and in which the note C was regarded as having an important melodic function. Many theorists of the period observed that B is used more typically than B in compositions in Lydian mode. Modern Lydian mode The Lydian scale can be described as a major scale with the fourth scale degree raised a semitone, making it an augmented fourth above the tonic, e.g., an F-major scale with a B rather than B. This mode's augmented fourth and the Locrian mode's diminished fifth are the only modes to have a tritone above the tonic. In Lydian mode, the tonic, dominant, and supertonic triads are all major. The subdominant is diminished. The triads built on the remaining three scale degrees are minor.