On New Year’s Eve, New York’s Metropolitan Opera will debut a new work in an unusual genre: It might be described as an opera mash-up.

“The Enchanted Island” is a pastiche of existing Baroque music written by composers including Handel, Vivaldi and Rameau. It’s also a mixture of two Shakespeare plays, woven together by creator and writer Jeremy Sams: The two central couples from “A Midsummer Night’s Dream” are shipwrecked on an island containing characters from “The Tempest.” Baroque expert William Christie conducts.

The cast includes starry names including Plácido Domingo as Neptune and Joyce DiDonato as the sorceress Sycorax. But there’s a lesser-known show-stealer lurking in the role of Caliban: bass-baritone Luca Pisaroni. In his most recent Met performance—as the servant Leporello in Mozart’s “Don Giovanni”—Mr. Pisaroni, 36, drew enthusiastic praise for his smartly comic portrayal and full-bodied sound.

Now preparing for this new-yet-old opera, Mr. Pisaroni is enjoying the freedom that the Baroque style affords. “At that time, composers were not so precise about what they wanted,” he said. “It leaves the performer a huge amount of possibility to do what they like in the moment.”

Born in Venezuela and raised in Parma, Italy, Mr. Pisaroni made his professional debut at age 26 in 2001. During his early training, he thought initially that he would be a tenor, but his voice developed a deeper sound. “I was disappointed because I knew a lot of tenor arias by heart,” he said.

The upside emerged quickly. “I’m right in the middle. I don’t have the high notes of the baritone, and I don’t have the deep notes of a bass. But the range and color is special,” he said, which lends him breadth within the bass-baritone repertory. “The characters are incredibly complex. You can portray kings and demons and gods. There is nothing better than that.”

– Pia Catton