Alleluia.

It the only word soprano Kathryn Mueller sings in the 3 1/2-minute final movement of Mozart's "Exsultate, jubilate."

Over and over again. A single word, stretched into a virtuosic, crowd-pleasing workout.

"This is really a showpiece for soprano," says Mueller, who will perform it as part of the Tucson Chamber Artists all-Mozart season opener this weekend. "The beginning and ending are fast. There's this recitative in the middle that's slow and beautiful, very contemplative and lyrical. It's a nice contrast, and you get to come back and sing the alleluia over and over again."

Mueller, a regular with the TCA since Eric Holtan started the professional choir in 2004, first sang "Exsultate, jubilate" when she was in college.

"It was actually one of the first big solo pieces I did at (Brown University in Providence, R.I.)," she said. Her performance in fall 1999 landed her a solo spot with the Brown orchestra.

Mozart wrote the choral piece in Italy when he was 16 years old for the famous Italian castrato Venanzio Rauzzini, who had been in Mozart's opera "Lucio Silla" a year earlier. A few years later, Mozart revisited it, working it into a piece suitable for soprano.

This weekend's performance comes on the heels of Mueller, 32, performing Samuel Barber's "Knoxville: Summer of 1915" with the Santa Fe Pro Musica in New Mexico last weekend. Later this month, she makes her debut with the Bach Collegium San Diego.

Mueller, who earned her master's from the University of Arizona and taught for several years with Tucson Unified School District's Opening Minds Through the Arts program, has been making a lot of debuts around the country this year.

"So far I'm not tired of the travel," said Mueller, who spent part of the summer of 2009 touring Indonesia with the Swara Sonora Trio - a trio that includes fellow OMA instructors baritone Nathan Krueger and pianist Aryo Wicaksono. "I've always wanted to be a singer since I was 6 ... so it's pretty exciting."

Her résumé now includes appearing as a soloist with the Washington Bach Consort, Santa Fe Pro Musica, Firebird Orchestra, Tucson Symphony Orchestra, Atlanta's New Trinity Baroque, Musica Sonora and TCA, with which she will perform Bach's B Minor Mass in February. She also has performed opera roles with Arizona Opera and the Seattle Academy of Baroque Opera.

Mueller, whose family owns the Canelo Hills Vineyard and Winery in Sonoita, has several Tucson dates upcoming, including appearing with her trio Les Sirénes in an Arizona Early Music Society recital in November.

This weekend's concert also includes Mozart's Double Violin Concerto, featuring the Tucson Symphony Orchestra's concertmaster Aaron Boyd and associate concertmaster Carla Ecker. It's the first time the pair has performed together outside the TSO.

Ecker described the piece as "very charming and not extremely profound."

"But it has some nice melodies in it, and it's a lot of fun," she said.

The concerto casts the twin violins in solo roles, but also gives solo passages to the cello and oboe.

"It's kind of a group effort," Ecker said.

If you go

Tucson Chamber Artists "Majestic Mozart."

• Featuring: Violinists Aaron Boyd and Carla Ecker and soprano Kathryn Mueller.

• When and where: 7:30 p.m. Saturday at Catalina Foothills High School Auditorium, 4300 E. Sunrise Drive; 2 p.m. Sunday at Grace St. Paul's Episcopal Church, 2331 E. Adams St.

• Tickets: $20 and $30 at the door or through tucsonchamberartists.org

• Details: 401-2651.

• All-Mozart program:

Double Violin Concerto.

"Exsultate, jubilate."

"Coronation" Mass.

Contact reporter Cathalena E. Burch at cburch@azstarnet.com or 573-4642.