On a normal day, the lower level of the Thompson Center in Chicago is like any other food court.  But Monday afternoon, a sort-of classical flash-mob transformed the space from dining hall to concert hall.

Soprano Renee Fleming and cellist Yo-Yo Ma led a chorus of Chicago high school students and Chicago Symphony Orchestra musicians in the performance. The show opened up with a call-and-response piece by students from Lake View High School, Chicago High School for the Arts and Merit School of Music. Then Ma and Fleming appeared and performed a piece together, accompanied by a pianist.

For most people, the event was a total and complete surprise. Some audience members had received an email from the CSO that some sort of concert was going on, but they had no idea who would be performing.

The group then performed a second song for the audience, “America, the Beautiful.” Ma, Fleming and the students were accompanied by musicians from the CSO for this number and encouraged diners and onlookers to sing along. The performance was part of Citizen Musician, an initiative run by the CSO that calls on musicians to use their talents as community-building tools.

“We do believe so much in the importance of music and the arts not just in the concert hall, but in our everyday lives,” Ma said.

The food court has since returned to its normal state.