The fourth-century BC Mausoleum at Halicarnassus was one of the Seven Wonders of the World. It lasted for centuries before being destroyed in an earthquake. If you go to the British Museum you can see two statues, larger than life, which might be of the eponymous Mausolus and his sister-cum-wife.

It’s the latter who is the subject of Cavalli’s opera. The historical Artemisia was renowned for her devotion: it was said that she mixed the ashes of Mausolus into a drink, so as to prolong their union. In the opera, Artemisia mourns the death of her husband and swears to marry the man who catches his murderer; but she has already fallen in love with “Clitarco”, not realising that he is Meraspe, who killed Mausolus (by accident, Meraspe says).

If you are already confused, hang in there, because it gets worse. Having two characters with near-identical names doesn’t help (even the libretto printed in the booklet gets in a muddle on the last page). In brief, then: Artemisia loves Meraspe, and vice versa; Ramiro loves Artemia but she too loves Meraspe; Artemisia is also loved by Alindo, whose deserted fiancée Oronta has disguised herself as a man. Then there’s a comic subplot for the servants.

The characters come and go in a series of short scenes. The preponderance of high voices makes it hard to tell the characters apart, so it’s essential to follow the libretto. The music is terrific and so is the cast. The singers are especially adept at putting across the dialogue, which has the vigour of a staged performance. Cavalli is prodigal in his provision of laments: the opera opens with Artemisia at the Mausoleum, and there’s a particularly fine example for Artemia, “Ardo, sospiro, e piango”. Both singers sometimes “bend” their notes expressively.

The orchestra is perfect: six plucked continuo instruments plus single strings, which accompany some of the arias. The booklet could do with a synopsis; and, eight centuries before Mohammed, “Scitico” can hardly mean Shiite (the reference is to a Scythian arrow). But this is a triumph for Claudio Cavina and La Venexiana.