Lydian.

The common name for the fifth of the eight church modes, the authentic mode on F. In the Middle Ages and Renaissance the Lydian mode was described in two ways: as the diatonic octave species from f to f', divided at c' and consisting of a third species of 5th (tone–tone–tone–semitone) plus a third species of 4th (tone–tone–semitone), thus f–g–a–b–c' + c'–d'–e'–f'; and as a mode whose Final was f and whose Ambitus was f–f' (or f–g'). In addition to the final, the note c' – the tenor of the corresponding fifth psalm tone – was regarded as having an important melodic function in the fifth church mode.

The Lydian mode was anomalous in two respects. First, the ambitus of each of the other authentic modes, Dorian, Phrygian and Mixolydian, was reckoned as beginning from its subfinal, which lies a tone below the final. But the note below the final of the Lydian mode, e, makes the interval of a semitone with the final, and ‘because of the deficiency below of [that] semitone’, as Guido expressed it in chapter 13 of the Micrologus (1025–6), the final f itself was normally stipulated as the lower limit of the mode. Second, despite the theoretical scale type of the Lydian, in particular its third species of 5th f–g–a–b–c', theorists from as early as Hucbald (De Harmonica Institutione, ed. C.V. Palisca and trans. W. Babb, New Haven, CT, 1978) recognized that in fact it is b rather than b that is characteristic in the two F modes, and even more so in the Hypolydian than in the Lydian. Similarly, according to chapter 15 of the Dialogus de musica attributed to Odo (GerbertS, i, 261), ‘in the fifth and sixth [modes] the first ninth degree b [reckoned from A] will prevail’, thus attesting to the prevalence of b rather than of b, the ‘second ninth degree’. Phrases in the lower part of the octave f–f' are more likely to use the fourth species of 5th (tone–tone–semitone–tone), which gives b on the fourth degree (for this reason one invariably finds b, rather than b used in the Hypolydian mode). Marchetto da Padova, in the Lucidarium of 1318 (ed. and trans. J.W. Herlinger, Chicago, 1985), gave the following rule of thumb for the use of b in the Lydian mode: ‘we should sing with b when the notes of the fifth tone [i.e. mode] are around c' and do not descend below a’ (bk 11, chap.4).

In Renaissance polyphony a great many compositions end on an F major triad, with parts ranging more or less within the Lydian and Hypolydian ambitus and with prominent cadences on C and A, as well as on F. With rare and special exceptions, these pieces are set in cantus mollis (i.e. with a one-flat signature); but here the use of cantus mollis does not denote a transposition of the mode up a 4th, as it does in pieces ‘in G Dorian’. Rather, it denotes the prevalence of B over B in the F modes. The 16th-century theorists who promulgated the theory that there were 12 modes in music, rather than the traditional eight of Gregorian chant, considered F-mode pieces in cantus mollis, however, as transpositions up a 4th from the C modes (Ionian and Hypoionian). Both Glarean (Dodecachordon, 1547, iii/16) and Zarlino (Le istitutioni harmoniche, 2/1573, iv/18) cited Josquin’s five-part Stabat mater, an F-mode piece with a one-flat signature in all voices, as an example of the transposed Ionian. But for the most part 16th-century musicians thought of F-mode pieces in cantus mollis as being in the Lydian or Hypolydian mode in the traditional system of the eight church modes. In modally ordered sets of pieces, they are found between the E-mode and G-mode compositions. For instance, of Palestrina’s modally ordered settings of stanzas from Petrarch’s Vergine canzone no.266, which comprise nos.1–8 of his Madrigali spirituali (1581), nos.5–6 are F-mode compositions in cantus mollis with higher voice ranges. No.5 has higher voice ranges, corresponding to the authentic Lydian mode, indicated by Chiavette; no.6 uses standard clefs to indicate the lower range of the plagal Hypolydian mode.

In the 19th and 20th centuries composers often used exotic scales and harmonies foreign to the conventional tonal major and minor modes to evoke peasant, nationalistic, mysterious or religious associations. One of the earliest such evocations is the slow movement of Beethoven’s Quartet op.132, which bears the inscription ‘Heiliger Dankgesang eines Genesenen an die Gottheit, in der lydischen Tonart’. Its principal sections are set in F, but without a key signature; the consistent use of B (usually in secondary dominant harmony), together with an avoidance of accidentals throughout each of the principal sections, give the tonality its Lydian character.

Modern scholars use ‘Lydian mode’ to designate the scale type of a folksong or non-Western melody that uses the modern major scale with the fourth degree raised by a semitone.

For the early history of Greek-derived modal names see Dorian. See also Mode.

HAROLD S. POWERS