Early opera was created by the changing demands of composers, soloists and impresarios; "the work" as such hardly existed at all. So here extracted from a bundle of surviving Venetian material is a "new" opera by Vivaldi – well, much of it is probably his, though only two acts out of three remain, parts have to be added, and some music may be by the little-known Giovanni Ristori. It contains some extremely effective music, bracingly performed by Federico Maria Sardelli's lively Italian period-instrument group Modo Antiquo and soloists, among whom Roberta Mameli's lustrous soprano shines in one tiny, brilliant aria that steals the show.