The Mars Volta’s second album has only five songs, but one of them, “Cassandra Gemini,” is a 33-minute epic. (The 14-minute title track is an important part of the picture, but you can only find it as a B-side of the single, “The Widow.”) Their first full-length, De-Loused In The Comatorium, was successful enough that they were able to say “yes, now double it” to pretty much every idea they had. More double-time Santana storms; more ultra-complex, densely orchestrated prog (now with strings); more sounds from across the Latin diaspora (songs in Spanish, salsa rhythms, a guest appearance by legendary pianist Larry Harlow); longer guitar solos from Omar Rodriguez Lopez; higher falsetto shrieks from vocalist Cedric Bixler-Zavala…frankly, it’s a bit much, even before you add in the street noise, sound effects and ambient atmospheres. But ultimately, their ambition pays off.