A decade ago, San Francisco investment banker Warren Hellman had a wacky idea: he wanted to underwrite a free bluegrass festival in San Francisco's Golden Gate Park.

"We had no idea whether anybody would show up," Hellman recalled from his office, with views of Angel Island. "And there were 20,000 people."

The 10th annual Hardly Strictly Bluegrass concert, which has grown wildly since its inception in 2001, will take over Golden Gate Park from Friday, Oct. 1, through Sunday, Oct. 3

"People are coming from all over the world. Interest is compounding," said Hellman, a managing director at San Francisco equity firm Hellman & Friedman.

There are all sorts of acts, from soul to Klezmer to rock, but the festival still seeks performers with more talent than fame.

Joining old-time bluegrass stalwarts Doc Watson, Hazel Dickens and Earl Scruggs are festival regulars Robert Earl Keen, Gillian Welch and Emmylou Harris.

Other bands sure to draw a crowd include Joan Baez, Elvis Costello and the Sugarcanes, Indigo Girls and Patti Smith.

And Hellman, 76, will play as well, picking the banjo with his band, the Wronglers. This is no novelty act. Hellman has diligently worked to learn his instrument, and now the Wronglers play all over the country.

Kinky Friedman will make his festival debut, the Texas country singer who this summer made his first West Coast appearances in 20 years. He's known for humorous and satirical songs like "They Don't Make Jews like Jesus Anymore." His band, the Texas Jewboys, will include festival regular Buddy Miller.

Friedman came to prominence in the mid-1970s when he opened for Bob Dylan. Today, many members of his audience are younger than his songs.

"They (young people) know me because I'm a folk hero, not a celebrity," Friedman deadpanned. "If I were a celebrity I'd be richer."

That's true of many of the acts on the bill — artists such as Richard Thompson, gritty SteveEarle and quirky Jonathan Richman (you saw him play guitar on the sidewalk in "There's Something About Mary").

During the three-day festival, 82 bands will perform on six stages throughout the park. The crowd has grown every year, to 800,000 over three days last year, according to San Francisco police and fire officials.

That's more than the population of San Francisco, Hellman noted, which makes it hard to quickly get from stage to stage, an issue some attendees have complained about.

Festival co-producer Dawn Holliday said they're doing all they can to keep the crowds moving.

John F. Kennedy Drive, the main road through Golden Gate's Speedway Meadow, will have temporary walls that make it impossible to see stages so people don't linger on the road. There will be added public transit plus more bike parking, and a marching band will troop up and down JFK Drive to keep festival-goers moving.

"People always follow a marching band," Holliday said.

The festival is beloved by musicians who enjoy the park's leafy setting and frequent jams.

"There are no sponsorships, no signage. It's like going to heaven," alt-country troubadour Robert Earl Keen said last fall. "I look forward to it all year long."

"We just love it," said 86-year-old banjo player Earl Scruggs, who may be best known for the "Beverly Hillbillies" theme song. "We love those spontaneous (jams) with other musicians. That's part of the fun."

Emmylou Harris, the silver-haired chanteuse who traditionally closes the festivities on Sunday, plans to perform with several other bands during the weekend, Hellman said.

And Robert Plant, the voice of Led Zeppelin, will join other musicians even though he's not listed as part of the lineup.

Scruggs' son Gary Scruggs, who plays in his dad's band, said Hellman's festival is a "wonderful gift to the city." It's a boon to the entire world of bluegrass, helping to elevate the careers of many.

Yet the eternally modest founder and funder sees the festival as a kindness to himself.

"People keep saying thank you, thank you, but this is the world's most selfish gift," said Hellman, who has set up a fund to ensure the festival continues for many years to come.

"To spend three days with people I adore and musicians I'm nuts about, it's an unbelievable mitzvah to be in a position to do this."

Michael Shapiro writes about music and theater for The Press Democrat.