Hot Buttered Rum have been described as a rock band playing bluegrass instruments (the bandmembers themselves call what they do "high altitude California bluegrass"), and with musical influences ranging from blues, rock, and jazz to Celtic and old-time string band music from the Appalachians, the group could almost be termed bluegrass fusion. The group was formed after Zachary Matthews (mandolin, fiddle) and bassist Bryan Horne's band Oversoul did some unplugged gigs. Matthews and Horne liked the sound and energy of playing acoustic, and after a one-month hiking tour of the Sierras in 1999 with Nat Keefe (guitar) and Erik Yates (banjo, guitar, Dobro, ukulele, flute, clarinet, sax, accordion, piano), the four returned to the Bay Area and formed the Hot Buttered Rum String Band, adding Aaron Redner (fiddle, mandolin) as a fifth member. The group released a live album, Live at the Freight and Salvage, in 2002, followed in 2004 by In These Parts, which was recorded in Fairfax by engineer Dave Dennison. The group shortened its name to Hot Buttered Rum for 2006's Well-Oiled Machine, which was produced by Mike Marshall and featured guest spots from Peter Rowan and Darol Anger. Live in the Northeast, with tracks drawn from various shows on a 2006 tour, was released in 2007.