There aren’t very many bluegrass bands that achieve headlining status at a hallowed rock hall like the Fillmore. But every now and then a “newgrass” band rises up to that next level. So it seemed only appropriate, on a weekend when the Yonder Mountain String Band had advanced to headlining San Francisco’s Warfield Theater on Friday night, that Hot Buttered Rum would headline the Fillmore on Saturday night. Hot Buttered Rum had previously headlined the Fillmore, but keeping the momentum going is the name of the game. The band went out of their way to do just that by flying cross country from a gig in New York City the previous night to make it back to their home base of San Francisco in time to headline a “groovy dance party,” as the show is billed. An apt double bill is opened by Poor Man’s Whiskey, who start the show with a strong set that, like Hot Buttered Rum, combines a rock attack with some bluegrass instrumentation for a high-energy sound. The band’s diversity is highlighted by superb covers of Aerosmith’s “Sweet Emotion” and the Grateful Dead’s “Terrapin Station.” The hyped-up Saturday night crowd welcomes Hot Buttered Rum to the stage like the hometown heroes they are, and the good time vibe is visibly in effect. “Spider” is the first tune of the set to really take off, with guitar, banjo, and fiddle all going wild, yet it’s a controlled frenzy. Guitarist Nat Keefe picks the main melody while banjo player Erik Yates supports him with a supporting rhythm and fiddler Aaron Redner adds in yet another layer on top; meanwhile, mandolin player Zachary Matthews and upright bassist Bryan Horne hold down the rhythm. A brief commentary acknowledging the full moon and a happy Passover leads into “Hugs, Not Handshakes”, a melodious groove with Redner providing the lead melody as he frequently would throughout the evening. The lyrics of “I feel the sun upon my face, in San Francisco, California, I feel the sun upon my face” strike a definite chord with the crowd. The song’s laidback yet melodiously jamming sound has an infectious vibe. “Banjo Rock ‘n’ Roll” kicks the dance party into high gear with a ’50s style rave-up led by Yates on the banjo, of course. The tune recalls any number of classic Chuck Berry tunes, yet sounds fresh with the Hot Buttered treatment. Redner delivers a smoking solo on the fiddle that gets the whole Fillmore twisting. The band references their New York gig with fellow San Franciscans Tea Leaf Green at a Rex Foundation benefit show the previous night before launching into “Always be the Moon”, a melodic, mid-tempo tune featuring some soulful group vocals. Matt Eakle of the David Grisman Quintet joins the band on flute to begin the second set, and “Song in a Can” gets the dance party going again, with melodies reminiscent of Paul Simon’s “Kodachrome”. The good time vibe is back in gear as the band steams forward with “Satisfy My Soul” and “Guns or Butter”, which keeps things moving with brisk rhythms that set the stage for a Wild West-type instrumental duel. The band’s precision and virtuoso musicianship is clearly on display, yet it’s combined with a freewheeling spirit that conjures visions of drunken saloon gigs from a bygone era. “Sweet Honey Fountain” finds its way into one of the evening’s deeper jams, which leads into “Silas” and “Waterpocket Fold” before jamming back into “Fountain”. “Queen Elizabeth” is dedicated to late, great promoter Bill Graham (as seems de rigueur these days), and features a melancholy vibe that recalls the aching beauty of the Rolling Stones’ “Wild Horses”. Later, the Beatles’ “I’ve Got a Feeling” gets the room grooving once more, as the triumphantly rocking vibe of the Fab Four resonates across time and space, with Zachary Matthews providing some extra oomph by moving from mandolin to drums. An encore of “(You Make Me) Feel like Dancin’” sums up the evening appropriately. Aaron Redner’s fiddle once again reigns supreme as the musical element that rises above and takes the band’s sound to that higher level, sending the crowd out into the evening floating on a Hot Buttered cloud.