Even those new to Sugarloaf Ridge State Park might expect to find the rolling hills, wooded trails and bucolic camping sites that have long made it a jewel for local hikers and bicyclists. Hearing the song “Soul Man” echoing through the trees, not so much.

But that’s what they would have heard Friday night as the band Rosetown Soul and R&B Revue kicked off its “Funky Fridays” performance at the park’s amphitheater before a packed crowd who came to dance and party under the sky and support the local park at the same time.

“It’s hard to imagine a more spectacular setting,” said Lou Kinzler of Santa Rosa who came with his wife, Olivia. They brought their own chairs and a cooler full of goodies including homemade banana nut muffins. “I get excited about this place every time I come up here.”

Many in Friday night’s crowd were regular hikers who wanted to give back to the park, which was slated to be closed until a nonprofit group stepped in to manage it and other state parks facing similar fates.

“I really felt it was something I should do,” said Lora Pritchard of Sebastopol, who said she has been a member for the last four years of an area club that has been leading local hikes for three decades. “But the shows have been great. It’s a beautiful place to listen to music.”

The amphitheater, which can accommodate about 300 people, sits near the top of the park, set against the backdrop of hills and trees and hiking trails that rise up to the peak of Bald Mountain, which on clear days can offer views of San Francisco Bay and Mount Diablo.

Nonprofit groups that have assumed management of state parks in Sonoma County, including Sugarloaf, have expanded entertainment options at outdoor venues to generate public interest in the parks and to help cover operating costs.

“The most dedicated hikers in the area come to Sugarloaf, as do the crazy bike riders who like to climb hills. But a lot of people don’t know it exists,” said John Roney, who manages Sugarloaf as an employee of the Sonoma Ecology Center, the lead partner in the team that oversees the park’s general operations.

He said the outdoor concert series at Sugarloaf, which wraps up next Friday with a performance by A Case of the Willys, has attracted a diverse crowd that he hopes will be inspired to pay return visits to the park.

The concert series is on pace to raise about $23,000, which would be a relatively small amount of the park’s $330,000 budget. But Roney said the money will help the park with its needs, which he said include a four-wheel-drive pickup.

“The cushion is making us comfortable writing the check,” Roney said.

In addition to “Team Sugarloaf,” nonprofits operate Jack London State Historic Park near Glen Ellen and Austin Creek State Recreation Area in Guerneville. The groups stepped in under a law that allowed the state to negotiate with nonprofits, private concessionaires and other groups to try and keep open 70 state parks that had been slated to shut in 2012.

The three parks rely mainly on day-use fees, venue rental, concessions and — in the case of Sugarloaf and Austin Creek — camping fees to meet operating budgets. But outdoor events such as Funky Fridays also have become an important source of profit.

At Jack London, “Broadway Under the Stars” has turned into a big hit, bringing top-flight talent from New York and Hollywood for Broadway-inspired concerts at the winery ruins next to the famous author’s home and at other venues. The series, which concludes with a gala celebration Sept. 5 and 6, last year drew more than 10,000 people. USA Today named it one of the nation’s top music venues.

“It’s absolutely wonderful. It’s songs. It’s dances. It’s under the stars. It doesn’t get much better,” said Tjiska Van Wyk, executive director of Jack London Park Partners, which is operating the park under the auspices of the Valley of the Moon Natural History Association.

The park also hosts a sundown music series Thursday evenings in the summer, as well as paid hikes. Combined, the special events cover about $100,000 of the park’s operating budget of about $600,000, Van Wyk said.

Van Wyk said California State Parks didn’t have the resources to organize such events.

“We have the staff to execute this,” she said. “We’re up to 400 community volunteers who are helping with these events.”

The nonprofit has signed an agreement with Transcendence Theatre to keep Broadway Under the Stars in the park through 2019.

At Austin Creek, Stewards of the Coast and Redwoods is gearing up for the Old Grove Festival on Sept. 13. The event, which features popular Bay Area band The Mother Hips, is held at the historic Redwood Forest Theater in Armstrong Redwoods.

The festival predates Stewards’ assuming management of Austin Creek. But Michele Luna, the nonprofit’s executive director, said the event has gained in importance because it’s the agency’s biggest fundraiser of the year, bringing in about $20,000.

The park’s annual operating is budget about $594,000.

Luna said the festival and other revenue-generating events the park hosts are about more than just raising money.

“It’s about getting people engaged with the organization,” she said. “From these (events), we get people aware of what we’re doing. They may become donors. They may become volunteers.”

Stewards handles day-use fee collection for Austin and for Armstrong Redwoods State Park and gives a portion of the proceeds to California State Parks.

Friday night at Sugarloaf, revelers came with their own food and wine, though there was a small concession stand where they could buy burgers and hot dogs. An area in front of the band was set aside for people to dance.

Park residents, such as a family of acorn woodpeckers, took in the entertainment as well.

“They’re regulars,” said Bill Myers who, with his wife Linda, organizes the concert series. “It’s part of the charm of this place. It’s wonderful.”

Staff Writer Elizabeth M. Cosin contributed to this report. You can reach Staff Writer Derek Moore at 521-5336 or derek.moore@pressdemocrat.com.