Nobody does special projects quite like Cecilia Bartoli – each one with at least a few premiere recordings, and each seemingly more elaborate than the last. Mission is no exception, having been preceded by a whimsical YouTube video series and even inspiring a new book by American detective novelist Donna Leon. The centre of all this activity? Agostino Steffani: composer, priest, diplomat and possible spy, whose name has fallen into obscurity but who, according to Bartoli and company, might just be the “missing link” between Monteverdi and Vivaldi in the development of Italian opera.

It’s hard to argue with their evidence. This double disc not only showcases Bartoli at her intense and virtuosic best; it’s an immersive musical experience, whose interest lies not merely in the novelty and rarity of the repertoire, but in its genuine brilliance. Gorgeous melodies, tireless musical invention, and a deft sense of theatre leap out at every turn (it’s hardly surprising to discover how heavily Handel was influenced by Steffani, even incorporating some of the latter’s compositions into his own works) and while the program is long, there’s little chance of fatigue.

Bartoli’s expressive palette is as colourful as Steffani’s own, and this music – much...