Several hundred members of the Stringed Instruments Geeks Union met Sunday night at the Garde Arts Center in New London to worship at the feet (and hands) of Joe Bonamassa and Sam Bush. It was in many ways a curious coupling: Bonamassa is the latest and best of the WBBDFSRV (White Boy Blues Dudes Following Stevie Ray Vaughan), while Bush is the multi-instrumentalist wizard who utilizes bluegrass as a template for all sorts of multi-colored, acousto-electric explorations. On one level, it's what us stringed instruments geeks live for. Raw choppage. But that both artists are fully rounded — fine composers, singers and entertainers — is a true bonus. Headliner Bonamassa and his group — bassist Carmine Rojas, keyboardist Rick Melick and drummer Bogie Bowles — ranged over his whole catalog, including the chart-topping latest CD, “Sloe Gin.” Blowtorching out of the gates with full-on electric blued-rock, including teasing quotes from Focus' “Hocus Pocus” and Deep Purple's “Perfect Strangers,” Bonamassa was the antithesis of bluegrass — yet immediately seduced the Bush fans with his genuine skill and passion. Bonamassa's version of Free's “Walk in My Shadows,” which he covered on his debut “A New Day Yesterday” album, was a wonderful fusion of futuristic blues-rock guitar and — as is too often overlooked — an emotive and impassioned vocal style that goes way beyond just screaming the blues. Too, his segue from “Sloe Gin” into “Woke Up Dreaming” literally left audience members dazed with disbelief. During their 50-minute set, the Bush Band — bassist Byron House, drummer Chris Brown, banjoist Scott West, guitarist Stephen Mougin — sprightly danced between pure archival bluegrass, hardcore country, delta roots, Nashvillean pop. On such tunes as “I Wanna Do Right,” “Bringing in the Georgia Mail” and a mind-blowingly lovely arrangement of It's a Beautiful Day's “White Bird,” Bush and his equally lightning-fingered boys proved a corn-whiskey equivalent of the Mahavishnu Orchestra. A favorite moment occurred when an audience member was overheard saying, “I didn't know a mandolin could go that fast.” The anticipated jam between the two giants was amazing yet, in a sense, anticlimactic. Bush and Bonamassa had performed such stunning individual sets that only a true gunfighters' showdown could perhaps be expected to further heighten the tension and pleasure. In the end, though, all nine players from both bands took the stage together to loosely explore four songs by J.J. Cale, Bob Dylan, B.B. King and a pretty astonishing take on the Jeff Beck Group's “Blues Deluxe.” All the players were given the spotlight — including dueling bass and drum solos — and all made the most of the opportunity. Ultimately, that Bonamassa and Bush share a sense of affection and respect for the musicians in their bands — and charitably wanted them to be part of the admittedly special moment — speaks highly of their spirit and sense of camaraderie. It was a privilege to see it unfold on what was the last of their shared four-date mini tour. In support, guitarist-songwriter Crosby Loggins, accompanied by his pal Sam Cartwright, who sang impeccable harmonies and boasts the violin prowess of Paganini, played a marvelously received 40-minute set of brainy acoustic pop.