Glancing through L.A. Opera’s 2015 schedule, one encounters a host of familiar names, from Verdi to Mozart and Rossini. Sandwiched between them, however, is a most unusual engagement that starts Thursday night and runs through the weekend: “Hercules vs. Vampires,” a new opera written by film composer Patrick Morganelli to accompany Mario Bava’s 1961 cult film classic “Hercules in the Haunted World.”

The premise might sound like the chintziest of gimmicks, but Morganelli has composed a serious piece, a complex 74-minute work performed live by a cast of nine singers and a 26-piece orchestra while the film silently plays behind them, singing from a libretto (also by Morganelli) that not only retains much of the film’s dialogue, but also synchronizes with the actors’ mouth movements.

“There’s a whole art to that,” Morganelli says. “Words have a shape and a rhythm to them that have a lot to do with the actual vocal line, and this had the additional burden of having to synchronize with the film. Plus, you have to give singers a vocal line that they can actually sing.”

Ccommissioned by a Portland company in 2009, “Hercules vs. Vampires” was well received on its initial run, but Morganelli decided he’d spent too long on the piece (six months, despite his first assumption it would take him six weeks) to let it “sit on a shelf in my studio.” After initial discussions with the American Cinematheque, he brought it to L.A. Opera.

“It’s not that there was pushback, but it took a while to get their arms around what it was,” he recalls. “But L.A. Opera, as an organization, is very adventurous and forward-looking, and even though they can do the standard repertoire with great success, they often seem to try to offer very different things to their audience.”

For his first opera, Morganelli drew on a multitude of inspirations, ranging from Ravel and Debussy to Penderecki and Ligeti, while making sure to avoid sword-and-sandal cliches – “big drums, trumpet fanfares” – and to refrain from letting the film’s camp appeal dictate the music.

“Obviously, this isn’t ‘The Bicycle Thief,’ but Bava was really trying to tell a serious story here. So my general sense about it was to do the same thing,” says the composer, who was a Bava fan going into the project. “Elmer Bernstein once said that sometimes you can achieve an amazing effect in a comedy if you score it very seriously. So I thought the unintentional humor in this film would be well-served by a score that takes it very seriously, and the net result would have its own wit or charm to it.”