NEW YORK — When Elizabeth DeShong comes onstage and sings her bravura opening aria in Rossini's "Semiramide," audiences at the Metropolitan Opera may be scratching their heads trying to recall when they've heard her before.

Indeed, her list of previous credits in the house make up a bewildering variety of styles and roles, from Suzuki in Puccini's "Madame Butterfly" to Hermia in Britten's "A Midsummer Night's Dream" to the First Norn in Wagner's "Goetterdaemmerung."

"I'm always being a surprise to people, and I get a kick out of that," the American mezzo said in an interview at the Met last month. "I like that I can be that chameleon, that I can give people something different every time."

As Arsace, the Assyrian commander in Rossini's 1823 opera, DeShong has by far her highest visibility and most challenging role to date.

"You need a combination of adrenaline and sort of a fighting spirit," she said. "You know you're in for a long evening ... and you just try to connect with the audience and give them the best product you can."

Hearing the bravos that greeted that first aria on opening night, she said, "gave me the energy for the rest of the evening. I felt like I had won the Olympics at the end, so it was good timing."

Though it's her first leading role at the Met, DeShong has performed major bel canto roles elsewhere (Rossini's "La Cenerentola" in Vienna and Donizetti's "Lucrezia Borgia" in San Francisco, to name two), drawing acclaim for her combination of burnished tone and coloratura agility. She had been set to star in Rossini's "L'Italiana in Algeri" last season at the Met until a throat infection forced her to cancel.

Her virtuosic talents will be on display, alongside soprano Angela Meade in the title role, on Saturday when "Semiramide" is broadcast to movie theaters worldwide as part of the Met's "Live in HD" series. [In the Berkshires, it will be shown at 1 p.m. at Mahaiwe Performing Arts Cehter in Great Barrington, Clark Art Institute in Williamstown and Beacon Cinema in Pittsfield].

The vocal fireworks required of a Rossini singer seem to come naturally to DeShong, and she gives much of the credit to her early training as a pianist, which made her comfortable writing her own ornamentations.

"I figure out what makes sense for the intention of the character," she said, "so it's not just embellishment for embellishment's sake. It has to be personal. Just adding notes with so much to remember, if you don't have a reason why you're singing that at the moment, then it's just noise."

For example, DeShong said, when Arsace is having a heroic moment, "then to me that doesn't call for multiple scales in repetition, or a flurry of notes. It has to be solid and sturdy, something that comes down maybe in an arpeggio, into that lower register to give a little bit of masculinity. Otherwise it doesn't read the right way."

DeShong made her singing debut in third grade in a school production of "Snow White." It wasn't a complete success, she recalled with a laugh: "I sang 'Whistle While You Work,' but I can't whistle, so that was a shame. The dwarfs had to whistle for me."

She continued studying both piano and singing, but decided on the latter as a career because "piano recitals made me terribly nervous.

"With the piano, if a note goes wrong, it's just a clunker and you take the abuse. You're silent," she said. "But with singing, you can face your audience head on, and you've got more you can say in the next measure."