There is some magical mystical force called musical chemistry that defines the line between mere entertainment and the transcendent ecstasy of a live, cathartic musical experience. Part one of the solution is the people on stage, of course, and they have to be mixed just exactly right to proceed. But part two is the crowd, and only with that igniting agent do you have an explosion such as was experienced during the two nights of Blue Mountain performances this past weekend. Blue Mountain was (is?) back, and there were a number of agents mixed properly to make it a memory etched in the brains of those in attendance.

A lot of what makes Blue Mountain so compelling is the combination of influences. At heart, they are a Rock Band, but incorporate country and blues and gospel and all of these other elements to produce Mississippi Music that defies categorization, as the best music does.

A few years back, we did a cover story for Honest Tune Magazine on a group of bands who did the same thing—mixed styles in a way that couldn’t be categorized. They played bluegrass instruments, but did so with a loose-limbed aesthetic that involved the merging of various musical styles and an improvisatory spirit. These bands followed the “New Grass” movement and led a new direction of what we coined as “Jam Grass.” These were folks like Leftover Salmon, String Cheese Incident, Yonder Mountain String Band, Blueground Undergrass and David Grisman.

Since then, other bands have taken the baton. But none as effectively as Railroad Earth. Named for a Jack Kerouac poem, Railroad Earth blends the patient performance approach of the Grateful Dead with the dexterous techniques of bluegrass blazers.

Over the course of three excellent studio albums, the group has amassed an impressive canon of songs that draw on bluegrass and jazz forms, wrapped neatly in a rock ‘n roll blanket. Their double-disc live CD, Elko, released last year, provides an excellent introduction to the band and their brand of improvisatory performance, featuring always-intriguing interpretations.

They quickly became a festival favorite after their formation in 2001, performing at Telluride Bluegrass Festival and Magnolia Music Festival, where I saw them for the first time in 2004. I was stunned then by their ability to dig deep into a song, and stretch it out to its limits, infusing it with the energy harnessed from the crowd, and from themselves.

They’re stopping off in Oxford on their way to another festival—the massive Bonnaroo—for what could be yet another memorable night in Oxford, one that I hope will have all the right ingredients and will be visited upon by that mystical force known as chemistry.

Touring Band Pick: Railroad Earth. Thursday June 14th. Proud Larry’s.

Local Band Pick: Slim Chance & The Oddbeaters. Thursday June 28. Two Stick. There’s nothing groundbreaking going on when this amalgamation of members of Shady Deal and Gunboat get together, but the enthusiasm and fun of playing simply for the sake of a good time is always contagious.