Bill Murray has been in town this week promoting the upcoming release of New Worlds: The Cradle Of Civilization, a documentary of Murray's classical music collaboration with cellist Jan Vogler filmed at the Acropolis.

The film is premiering at the Village East on Groundhog Day, but lucky onlookers got their own semi-private performance at Washington Square Park on Wednesday when Murray, Vogler and their collaborators performed a surprise set under the arch.

Murray and Vogler were joined by violinist Mira Wang and pianist Vanessa Perez for the short set of classical-and-spoken-word pieces, which included “It Ain’t Necessarily So,” Lawrence Ferlinghetti's “Dog," and two songs from West Side Story, "I Feel Pretty" and "America."

Videographer Nicholas Heller, a.k.a. New York Nico, was on hand for the performance, which he told Gothamist was pretty spontaneous.

"I was told about it the night before," he said. A friend of Murray's reached out to him to ask him to document the surprise performance.

"Bill was as nice and down to Earth as you would expect," he added. "There are not many big time celebs that would be do something like that. People were so excited to see him."

You can check out videos of the performance below.

According to Page Six, it wasn't just passersby in the crowd: also on hand were former Real Housewife Carole Radziwill, author and former Bronx detective Edward Conlon, and Karen Duffy, a producer of Murray's upcoming documentary.

After a few songs, the show was apparently broken up by police. “The cops say we have to turn off the microphones. Let’s rip this place apart!” Murray said before ending the set.

Here's a trailer for the documentary below.

Murray and Vogel first toured the New Worlds project back in 2017. At the time, we wrote that the project included a range of music "from Stephen Foster’s 'Jeanie With the Light Brown Hair' to Van Morrison to songs from West Side Story; he also reads spoken word passages from Walt Whitman and Ernest Hemingway over Schubert and Bach pieces."

Murray and Vogel also dropped by All Of It earlier this week—you can hear them talk about the New Worlds projects below.