THE Mars Volta’s dense show of prog-rock at the Roseland Ball room Friday revealed just how outside these boys are.

Latin jazz, hard-core punk and psychedelic rock mixed during the 2 1/2-hour performance. Songs melted into one another without break or even slight cracks in the band’s wall of sound. A devoted Volterian listening to the melange would probably be able to deliver a set list, but to the uninitiated it all sounded like one very long jam.

The band’s masterminds, vocalist Cedric Bixler-Zavala and guitarist Omar Rodriguez-Lopez hit the stage running at this important New York show. The sold-out house was testament that their bizarre sonic aesthetic, which defies the rules of rock, does, in fact, have commercial potential.

At Roseland, the performance was extremely energetic, especially that of Bixler-Zavala, who worked the stage and the scales like a young Robert Plant. During a number of blues-rock passages in the music, it seemed as if he was on the verge of breaking into Led Zeppelin’s “Whole Lotta Love.”

A Mars Volta jam can cut through a blues rock riff or a jazz bop, or scream like progressive metal.

For those chomping on mushrooms and coherent enough to connect the musical dots, the jams, which sometimes extended to 20 minutes, were probably thrilling experiments in improvisation.

Jams can go bad, too.

At times the Mars Volta seemed to be creating tunes as if they were raining notes. The assault, sometimes atonal noise for the sake of noise, wasn’t totally appreciated by the New York house.

This is a band that likes to challenge itself and, in turn, the audience. Still, the Mars Volta should consider just how difficult their music is and make the live shows a little more interesting – and accessible – with a high-tech light show that would complement the sound and draw those in the rear of the theater back into the music.