Francesco Melzi came into Leonardo’s life in around 1505. This young man, by contrast, was from a noble Milanese family, and developed a role in the workshop akin to private secretary. He and Leonardo soon developed a closer intimacy that Mills and Mullin liken to father and son. Melzi was, as Mullin notes, “completely different from Salaí in his social standing and his demeanour.” No cheeky nicknames for the aristocratic Melzi: he was addressed by Leonardo as ‘Master Francesco’.

While Mills’s music for Leonardo is of course contemporary, it has been scored for a viol consort - that is, an ensemble of players of the viol, a stringed instrument evocative of the early 16th Century. Mullin’s libretto is drawn almost entirely from historical sources, most important of which were Leonardo's own notebooks, which the left-handed artist wrote in mirror script.

The opera charts the “shifting triangle that Leonardo had with these two young men,” says Mullin. “Leonardo moves from one relationship to the other, and Salaí gets a bit pushed out.” Late in life Leonardo moved to France, with both male companions in attendance, but Salaí returned to Milan, and was not there at the master’s bedside when he died in 1519. “Leonardo leaves him very little: he’s left only half a vineyard, which is odd,” says Mullin. Melzi, by contrast, inherited Leonardo’s notebooks and many of his paintings. “It seems there was a private drama that had been playing out from one figure to another.”

His male muse

As historic characters, Salaí and Melzi come down to us through Leonardo's depictions of them in word and image – both men were noted for their beauty, and Salaí is thought to be the model for the paintings Bacchus and Saint John the Baptist. To both composer and librettist, the relationships appear to have been more intense and profound than simply artist and assistants. “Leonardo draws Salaí so much, it’s not hard to say he was a muse as well,” says Mills. “Everyone considers him to have been Leonardo’s companion – he buys him expensive clothes, they travel together, everyone talks about how beautiful he was.”