Utah Opera had the coolest guest at its 40th-birthday party: Renée Fleming, arguably the best-known soprano in the world right now, thanks to her Grammy Award-winning recordings, crossover projects (including portraying a diva in a Broadway comedy) and status as the first opera singer to perform “The Star-Spangled Banner” at a Super Bowl. As if that weren’t enough, she’s been published in the Journal of the American Medical Association and has lately been giving multimedia presentations on music and the brain, as she did earlier in the week in Salt Lake City.

Fleming — who, contrary to what you might have heard, is not retiring from the opera stage but retiring some roles — showed that her opulent voice and personal charm haven’t faded as she headlined a festive and fun evening of opera and musical-theater favorites with the Utah Opera Chorus and Utah Symphony in Abravanel Hall on Wednesday night. (The orchestra and opera company merged in 2002.)

She took the stage with a beautiful interpretation of Richard Strauss’ “Four Last Songs.” Her delivery of the final phrase in the last song, “At Sunset,” was particularly exquisite. The orchestra, under music director Thierry Fischer, gave lovingly detailed accompaniment, though it might have done well to back off just a bit. Edwin Rollett’s horn solo in “September,” concertmaster Madeline Adkins’ work in “When Falling Asleep” and flutists Mercedes Smith and Lisa Byrnes’ depiction of the two larks in “At Sunset” were among the highlights.

Fleming also charmed the crowd with “Somewhere” and “I Feel Pretty” from Leonard Bernstein’s “West Side Story,” Margherita’s mad scene from Arrigo Boito’s “Mefistofele,” “O mio babbino caro” from Giacomo Puccini’s “Gianni Schicchi” and Ruggero Leoncavallo’s “Mattinata,” a concert aria popularized by such acts as the Three Tenors — but not before explaining the arias’ contexts in layman’s terms, to the delight of listeners. (The near-capacity crowd also exploded in cheers at the way the last word of “O mio babbino caro” floated over the hall.)

Even more captivating was her delivery of Björk’s “Virus,” spiced up by cool percussion riffs and a memorable trombone solo from Mark Davidson. Tenor Christopher Oglesby, a Utah Opera resident artist, was the Alfredo to Fleming’s Violetta in a delightful rendition of the drinking song from Giuseppe Verdi’s “La Traviata.”

The Utah Opera Chorus shone in the “Traviata” scene, an earnest reading of “The Promise of Living” from Aaron Copland’s “The Tender Land” and a full-throated performance of the Anvil Chorus from Verdi’s “Il Trovatore.”

The orchestra had fun with Bernstein’s snappy Overture to “Candide” and the high drama of Verdi’s Overture to “La Forza del Destino.” (Adding to the party atmosphere, the women of the orchestra dressed in colorful gowns, though the men unfortunately weren’t given the same latitude with their neckwear.)

The evening had the air of a public-television pledge drive via brief appeals from development VP Leslie Peterson, a daughter of Utah Opera’s founder, and other officials. (There was even a recent high school grad on hand to explain to attendees how to text in their donations.) A short video message sang the praises of Utah Symphony | Utah Opera’s education programs, which will receive all proceeds from the concert and associated festivities.

UTAH SYMPHONY | UTAH OPERA

The orchestra’s annual gala concert doubles as a celebration of sister company Utah Opera’s 40th anniversary and fundraiser for the joint company’s educational outreach programs.

With • Soprano Renée Fleming, conductor Thierry Fischer and the Utah Opera Chorus

When • Wednesday, Sept. 13

Where • Abravanel Hall, 123 W. South Temple, Salt Lake City