… the Suite (originally Symphony) in E (1903), in which distinctive Respighian phraseology is often foreshadowed. Here, as in Christus [composed at age 19], there are occasional signs that he was responsive to Gregorian chant long before he met his future wife, despite her oft-quoted claim that it was she who first induced him to study plainsong systematically.

Vetrate di chiesa, though it too is colourful and ostensibly pictorial, consists largely of orchestral amplifications of the abstract Tre preludi sopra melodie gregoriane for piano (1919–21).

The best known of the overtly abstract compositions whose use of plainsong-like material followed on from the Tre preludi is the Concerto gregoriano for violin and orchestra (1921), whose central movement features the familiar Easter sequence Victimae paschali. Elsewhere in the work the allusions to plainchant are more fleeting and disguised; the quasi-pastoral result parallels some of the more calmly modal music of Vaughan Williams. Likewise pervaded by freely plainsong-like themes are the long and rather diffuse Concerto in modo misolidio for piano and orchestra (1925), and the more impressive Quartetto dorico (1924), in which predominantly modal material is put to richly varied uses within a seemingly rhapsodic yet thematically unified single movement structure.

in Maria egiziaca ["The Egyptian Mary"] – originally designed for small-scale, semi-staged presentation in the concert hall but thereafter performed quite often in Italian opera houses – he matched Guastalla’s self-consciously archaic libretto with austerely evocative music in which Gregorian, Renaissance and Monteverdian influences are evident, alongside others of more recent origin.