Impresario and banjo enthusiast Hellman opened the Saturday morning session with his own band, the Wronglers, at the small Porch Stage right by the festival entrance.
Costello, featuring accomplices on banjo, mandolin and fiddles, caused pedestrian gridlock during his set Sunday afternoon at the far end of the festival site on the Star Stage, appearing back-to-back with rock poetess Patti Smith, who name-checked William Blake and Lawrence Ferlinghetti before she got through her second number.
Police estimated more than 600,000 attended the festival over the three days, including 350,000 Sunday, the festival's traditional top attendance day. Between the high-caliber talent and breadth of musical styles drawn from inside and outside the acoustic music world, the festival has undoubtedly become the greatest outdoor music festival anywhere.
Harris and Griffin likewise joined Miller for his Saturday set at the Rooster Stage, as did Jim Lauderdale, the Nashville-based songwriter who also played Sunday with Costello.
Randy Newman played the Towers of Gold Stage, while Dave Alvin and the Guilty Women were rocking leafy Marx Meadow from the Rooster Stage, including an impromptu reunion with his brother, Phil Alvin, who used to sing in their rock band, the Blasters.
Nobody has a better time than Hellman, who played banjo Sunday with Earl Scruggs on the Banjo Stage and backed up clog dancer Heidi Clare at the Porch Stage. Hardly Strictly Bluegrass might well be the Bay Area's biggest party.
Friday
Go ahead and wear your old "Hammer" pants to the festival; we dare you.
This 83-year-old banjo man has been making great music longer than most performers at this festival have been alive.
Saturday
# Trombone Shorty: What was the most-talked-about act leading up to this year's Monterey Jazz Festival? # Carolina Chocolate Drops: This authentic-sounding old-timey string band's mission is to perform and preserve traditional African-American music of the South (specifically, the Piedmont region of the Carolinas). The Chocolate Drops also perform Friday at San Francisco's Slim's ($15; www.slims-sf.com).
"Dream Attic" was partially taped back in February at San Francisco's Great American Music Hall.
Sunday
# Doc Watson: Nobody flatpicks a guitar like Watson. This 87-year-old Deep Gap, N.C., native's set should be an absolute clinic in authentic acoustic blues, folk, gospel and bluegrass music.
Dawn Holliday, the general manager of Slim's and Great American Music Hall, is on the phone with Warren Hellman. Patti Smith, Sharon Jones and the Dap-Kings, Randy Newman, the Avett Brothers and Rosanne Cash will be among the more than 70 acts appearing at the free festival Friday through next Sunday in Golden Gate Park.
Many of the Hardly Strictly regulars will also be on the bill, including Emmylou Harris, Ralph Stanley, Steve Earle, Del McCoury and Elvis Costello.
Ten years ago, Hellman, who is also an investor in Slim's, approached Holliday and her staff about putting on a little bluegrass festival in the park. "It's unreal that one man continues to support a festival of this size."