This was no running with the bulls in Pamplona, but for dozens of cello lovers, the chance to mingle - and play - with professional musicians from the Philadelphia Orchestra on Saturday was a thrill all its own.

The "cello play-in" filled the typically spare lobby of the Kimmel Center for the Performing Arts with musicians of all ages and skill levels. Also on hand, of course, were their parents, grandparents and teachers, indeed anyone who loves the sound of a cello in classical, pop and holiday music.

For a full hour, members of the orchestra's cello section sat alongside the amateurs, playing everything from Bach's haunting "Air on the G-String" and Handel's jaunty "Hornpipe" to singalongs like "Jingle Bells" and Paul McCartney's "Michelle."

"Awesome," said Heather Kohler of Lansdale, whose 8-year-old son Markese Williams - he of the mohawk haircut - was gingerly plucking the strings of the instrument he chose just four months ago, his mother said, "because his sister plays the violin and he wanted something bigger."

Whatever the back story, everyone seemed to have fun.

"It's about the pure joy of music-making," said Gloria dePasquale, an orchestra cellist since 1977, who serves as chair of the musicians' education committee and promoter-in-chief of the play-in.

The evening drew two special guests: conductor Gianandrea Noseda, music director of the Teatro Regio in Turin, Italy, and cellist Alisa Weilerstein, a 2011 MacArthur Foundation Fellow whose November debut album featured the Elliott Carter and Elgar Cello Concertos with conductor Daniel Barenboim and the Berlin Staatskapelle orchestra.

Both jumped right in for a good half-hour or more to play old favorites, even though they had star billing on the Philadelphia Orchestra's program immediately after the play-in. In fact, organizers of the pre-concert event hoped that their presence - and the play-in - would inspire a pumped-up audience to buy (discounted) tickets for the performance, called "Tchaikovsky and a Genius."

"We are able to measure the impact of these things now," dePasquale said, "and answer the question: 'Do these events drive up box office sales?' "

The anecdotal evidence was in. When asked how many play-in participants would be stashing their instruments in the Kimmel's "secure cello check" before heading for the orchestra, hands shot up all over the room.

Besides the "pure joy" factor, and potential ticket sales, there were other reasons for the play-in.

The orchestra is intently looking for ways to connect with the public, as it did this year with free concerts at Penn's Landing and Curtis Arboretum in suburban Wyncote.

And it's some feat when the Kimmel Center lobby becomes a destination, rather than dead space or pass-through.

Isabel Newell of Moorestown, a 12-year-old who's been playing cello for five years, said she was "only a little nervous" because she's performed before in summer camp and just landed the role of Annie Jr. in the kids' musical of the same name.

Isabel, outfitted in elegant black for the event, takes lessons from orchestra cellist Bob Cafaro, who calls her "a big talent." She claims not to practice much, but she does love the instrument.

"The cello is real cool, indeed," she said. "It has the most beautiful sounds."

When the call went out from the orchestra earlier this year for ideas for "one big community event that is low cost but big impact," dePasquale said she immediately thought of a cello play-in. The idea had been successfully tried once before, when the Kimmel Center opened more than a decade ago.

In late November, music schools, colleges and community orchestras in the Philadelphia area received an email blast invitation to the play-in and, according to Jesson Geiple, the orchestra's public relations manager, response was swift. In just a week, 164 people registered and the event had to be closed.

Participants were instructed to download a part for each of the 20 or so musical selections, according to their ability level.

Susan Clayton, 60, said she took up the cello only 15 years ago, after a health scare. "I find it mesmerizing, calming, peaceful," she said, which is useful these days, too.

For although Clayton is healthy, her house is not. "I live in Toms River," she said. "We're recovering from Sandy."

Contact Virginia A. Smith at 215-854-5720 or vsmith@phillynews.com.