About 20 University of Arizona School of Music voice students broke out in song Tuesday afternoon while riding the Sun Links streetcar.

Several times during a trip that started near the UA and wound its way downtown and south of Interstate 10 and back, the students burst into song. A pair of tourists was along for the full ride, with the wife capturing it on cellphone video. "We missed our stop three or four stops ago," the woman commented.

As the streetcar made the loop at El Mercado just after 4:30 p.m. Tuesday, two young boys and several older men boarded, including one man in a wheelchair who wheeled himself right into the center of the singers being conducted by UA Opera Theater interim director David Ward. The man looked about a bit confused but quickly settled into the notion that a group of pretty talented young people were serenading him with a song from Johann Strauss's "Die Fledermaus."

Although it was billed as a flash mob, it was more of a spontaneous serenade. Flash mobs are vocal events that unfold one unsuspecting voice at a time. Understandably, that's an impossible feat to pull off in the narrow confines of the Tucson streetcar.

Ward got a little help guiding his troupe of vocalists from Judi Hasbrouck, a member of the Opera Guild of Southern Arizona. The guild and the school are teaming up with for Opera on the Streetcar, a fundraising auction and reception Feb. 15 at the Screening Room

The event starts back on the streetcar at 3 p.m. with UA Opera Theater students once again randomly serenading strangers. The party moves to the Screening Room at 127 E. Congress St. at 4 p.m. for a live aria auction: bidders can decide which concert they want to bid on and the concerts are performed by guest artists including students.

The cost is $25 and that includes a Sun Links day pass and a wine and hor d'oervres reception. Order tickets here

Proceeds from ticket sales benefit the Opera Guild's programs to provide grants and scholarships to vocal students, as well as fund prize money for the guild's vocal competitions.