Opera people complain about the tiny extent of the established repertoire (writing good operas is not easy), so the marked absence of Christoph Willibald von Gluck from theatres feels rather wanton. He was a vital revolutionary, and without him Mozart could hardly have existed; his Orfeo ed Euridice (1762) crops up every so often, a piece as full of classical poise as a Poussin, but his 44 other operas – written by this German-Bohemian composer in the Italian and French models that ruled the world – you seek in vain.

Gluck does not give you the thrills of later Italian opera or the human richness of Mozart, but his music is astonishingly lovely. By the time of Iphigénie (1779), he had single-handedly returned opera from the corruption of Baroque indulgence to its ideal origins in Greek tragedy; this production highlights its qualities of extreme emotion expressed with the greatest restraint, in a form consciously striving to embody Enlightenment ideals of truth and reason.