Cloaked in a distressed-looking collage of an American flag that's crossed over by red and white stripes, Standards, the fourth album by post-rock torch-bearers Tortoise, can be viewed as both a battle flag and a battlefield. Since forming in 1990 in Chicago, the band has inventively blended jazz-influenced, sometimes improvisatory organic instrumentation with intensive studio treatments reminiscent at times of Jamaican dub, all executed with rhythmic precision. In the process, they have emerged as standard-bearers for an electro-acoustic scene that has developed around them; artists in such disparate scenes as minimal techno and loungey trip-hop owe a debt to Tortoise's influence.

With Standards, the group finds it has something even heavier than standards to bear: its reputation.

"It's frustrating to learn about unfair expectations placed on you by people," said Doug McCombs, Tortoise bassist and, along with John Herndon, one of the band's two remaining founders. "It was worse actually a few years ago when the term 'post-rock'" — which Simon Reynolds, its inventor, defined as "using rock instrumentation for non-rock purposes" — "was coined and we were supposed to be this band to destroy rock music or rock conventions. And, you know, that was never our intention at all. So you start to hear from people, 'Why do Tortoise want to destroy rock music? What's their problem?' And it had nothing to do with us at all. It was this invented thing." To be sure, Tortoise (which now consists of McCombs, Herndon, Dan Bitney, Jeff Parker and John McEntire) have had as many prefixes and suffixes attached to their sound as any other band today. Ironically, the more labels tossed in their direction — post-, prog-, quasi-, kraut-, -jazz, -funk — the fewer rules Tortoise seem to follow. A strong background in British post-punk (visionary early-'80s outfits like Wire and Gang of Four) and '80s hardcore links all the members, but only one, Parker, (a member of the Association for the Advancement of Creative Musicians), has direct ties to the jazz community; the deluge of free-jazz comparisons consistently confound the band. Never before, in fact, has Tortoise sounded more in touch with their rock roots than on Standards. "Seneca" opens the album with an anthem of a band struggling to detach itself from its perceived preoccupation with cut-and-paste studio assemblages. Compared to the lengthy, labored pieces of 1998's TNT, the new album is decidedly funkier, as on "Monica," and feistier, as on "Blackjack." "It's kind of akin to Presence by Led Zeppelin," Casey Rice said of Standards, via email. Rice has worked with the group as a producer and sound technician. "After their long arduous process of making a double album (TNT a.k.a. Physical Graffiti), they take a new view and make a direct, more concise rock record." Having been both glorified and vilified for their open approach to a variety of influences on past albums such as TNTand '96's Millions Now Living Will Never Die, is Tortoise wary of Standards being hailed as their "return to rock." "TNT was a lot of information and we definitely wanted to bring all of those songs to their logical end and use them on that record," said McCombs. "At the same time, we learned that it doesn't necessarily make an easy listen: it's not necessarily something people are going to want to listen to all the way through in one sitting. So we decided to make something that was shorter … more user-friendly." Bundy K. Brown, an original Tortoise member who left the group following its acclaimed self-titled debut (released in 1994), said the often emotionally opaque nature of their albums is no mistake. "I have a pretty good understanding when I hear a record or see them onstage what is one person's vision and what may have been arrived at more cooperatively," he said. "But I think that's difficult for others outside their peer group to perceive, and that's intentional. I think it is part of Tortoise's aesthetic to intentionally blur those lines."