Because of the importance of the major scale in modern music, the Lydian mode is often described (or learned) 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♭ (Powers 2001).
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 medieval and modern Ionian mode (the major scale) (Barbera 1984, 233, 240).
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 (Powers 2001).
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.
A rare, extended use of the Lydian mode in the Classical repertoire is Simon Sechter's 1822 Messe in der lydischen Tonart (Mass in the Lydian Mode) (Carver 2005, 76). A more famous example from around the same time is the third movement of Ludwig van Beethoven's String Quartet No. 15 in A minor, Op. 132 (1825), titled by the composer "Heiliger Dankgesang eines Genesenen an die Gottheit, in der lydischen Tonart" ("Holy Song of Thanksgiving by a Convalescent to the Divinity, in the Lydian Mode"). The alternating passages in F use the Lydian scale with sharp fourth scale degree exclusively.
Anton Bruckner employed the sharpened fourth of the Lydian scale in his motet Os justi (1879) more strictly than Renaissance composers ever did when writing in this mode (Carver 2005, 74-75).
In the 20th century, composers began once again to exploit modal scales with some frequency. George Enescu, for example, includes Lydian-mode passages in the second and third movements of his 1906 Decet for Winds, Op. 14 (Hoffmann and Ra?iu 1971, 319). An example from the middle of the century is the scherzo movement of Carlos Chávez's Symphony No. 3 (1951-54). The movement opens with a fugue subject, featuring extremely wide leaps, in C Lydian with following entries in F and G Lydian (Orbón 1987, 90-91).
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