Head of Femur RINGODOM OR PROCTOR (Greyday Productions)

The head of femur is a bone. And as the band who’ve named themselves after that bone explain, "when Elvis Presley appeared on The Ed Sullivan Show, the cameramen were instructed to film Elvis’s pelvis ‘no lower than the head of femur.’ Thus, the Head of Femur is the point where rock and roll becomes sex, and we balance on top of it!"

I’m not sure what kind of sex these Chicago-via-Nebraska tune tinkerers are into, but I’m guessing it ain’t vanilla, since these orchestral maneuvers in the dark — all euphonium and flügelhorn and handclaps, punctuated skittering stop-starts and echo-laden caesuras — represent rock and roll at the outer limits. A sorta supergroup built around the core trio of vocalist/guitarist Mike Elsener (Solar Wind), vocalist/keyboardist/drummer Ben Armstrong (ex–Commander Venus), and vocalist/guitarist Matt Focht (Bright Eyes) but augmented by more than a dozen friends playing strings and woodwinds and brass and electronics, HoF serve up songs that can be so busily intricate as to seem hardly possible from a 64-track — a googolplex-track maybe. Flecks of sound fly off in every direction: manic Zappa xylophones and burnished brass flourishes ("80 Steps to Jonah"); insistent organic-mechanical bass trills and island riddims with steel-drum flourishes ("Curve That Byrd"). But some tracks offer majestic washes of thrumming low end sprinkled with synthesized stardust and celestial harmonizing ("The Car Wore a Halo Hat"). And even the more ambitious numbers are undergirded by insidiously hummable melodies and infectious rhythms. So for every passage that sounds like Van Dyke Parks and Brian Wilson together in a washer on spin cycle, there’s another unorthodox anthem that evokes emo via Eno. The lyrics are often impenetrable to the point of being nonsense ("he gets psyched for birthday pitfall kitchen"?), but the music is all-enveloping, concocting chimerical sonic microcosms where even jabberwocky rings true like the King’s English.

(Head of Femur play this Monday, March 1, at Great Scott, 1222 Commonwealth Avenue in Brighton; call 617-734-4502.)