“I just want tonight to be, like, an orchestral process awareness night,” he said as he took the stage with the St. Louis Symphony Orchestra at Powell Hall.

For much of the concert, the pianist, singer and songwriter spent time between numbers greeting the orchestrators of his pop and rock songs, pointing out various facets of their arrangements and talking about the songs themselves.

Folds has performed several times with the SLSO, and it is always a pleasure to rediscover how his music, whose irreverence can make it seem simple, is suitable for an orchestra.

The SLSO, led by assistant conductor Stephanie Childress, brought the scores to life. Some have just been put into service.

“And the group? Folds said from the start. He praised Childress, various sections and concertmaster David Halen.

The audience also had a part to play, occasionally filling in vocal parts, beginning with the a cappella opener to the first song, “Effington”.

Scoring, Folds said, is “something you should leave to the professionals.” Before the song “Kylie From Connecticut,” he talked about arranging the piece himself on a long flight from the United States to Australia. Another arranger reworked it later but left the middle section untouched, which Folds didn’t like. This part, he joked, could be called “Drunk on the Plane”.

Some of the sheet music, Folds said, was done by Paul Buckmaster, whose work with artists such as David Bowie “defined the chords of 70s pop records.” One was for “Gracie,” a song written for Folds’ daughter.

The first set ended with “Fred Jones Pt. 2” and “Free Coffee”, the latter poking fun at the fact that now that he has money, people are giving him free stuff. When he was broke, of course, he had nothing.

And every song has been transformed from its pop setup into something more delicate, grand, or even comedic. The SLSO nailed them all despite having limited rehearsal time with Folds that day.

The orchestra faced an even greater challenge in the second half of the concert. One audience member called “Rock This Bitch” a fan favorite because it requires Folds to improvise both music and lyrics on the spot, with the added complication of having to invent parts for the orchestra to play. It earned him a standing ovation.

For “You Don’t Know Me”, Folds asked the audience to fill in the vocal parts sung on the recording by Regina Spektor.

“Not the Same” demanded even more singing from the audience. Folds directed from the edge of the stage, raising and lowering his arms to indicate height, even throwing in a few Bugs-Bunny-as-Leopold moves.

Earlier, Folds, a passionate advocate for the arts, spoke at length about their importance to society. A symphony, he said, is a symbol of civilization: it shows that a large group of people can work together to create something meaningful.

“A town sucks that doesn’t have a symphony orchestra, and this town has one of the best,” he said.

“Come back,” he urged the audience. “Promise me now while you’re drunk.”

Folds and the SLSO perform again Saturday night at Powell Hall.