CLEVELAND, Ohio - Sara Bareilles loves playing Cleveland. "I come here on tour, and Cleveland is one of my favorite places to stop - the audiences are ravenous," Bareilles told a packed State Theatre on Tuesday night.

That they are. The singer-songwriter was a surprise guest at the annual KeyBank Broadway Series launch party, in town to promote "Waitress," the musical she scored, and the first show in the 2017-18 lineup, which will kick off its national tour in Cleveland this fall.

The story centers on a Jenna, a pregnant young woman working at a roadside diner looking for a way out of her unhappy marriage. A pie-baking contest - and the cash prize that will go to the winner - just might be her salvation. Bareilles, nominated for a 2016 Tony for her music and lyrics, will headline the show as Jenna when star Jessie Mueller leaves the New York production at the end of March. (Bareilles will be with the Broadway cast through June 11.)

She appeared onstage - fresh from her moving "In Memoriam" tribute performance of Joni Mitchell's "Both Sides Now" at the 2017 Oscars Sunday night - and took a seat next to Gina Vernaci, Playhouse Square's executive producer, as the stunned crowd screamed with joy.

But she surprised the architect of the popular Broadway Series, too.

Though she was only scheduled to do a Q&A with Vernaci, a little more than two minutes into this video snippet of their chat, she decided to give an impromptu performance of "She Used to Be Mine," the 11 o'clock number from "Waitress."

"I promise we didn't talk about this," Bareilles said as she walked toward a keyboard that had been used to entertain the audience before the gala unveiling began.

"We didn't!" said Vernaci. "But here's a piano!"