Fifteen years after its self-titled debut, in what we might now call the "post-post-rock era," the automatic waves of hyperbolic praise that once greeted any new release from the Chicago instrumental collective Tortoise have ebbed, and it's become much easier to hear the band as what it always was: A group of progressive-rock geeks who happened to understand that a good groove beats pointless displays of virtuosity every time, crafting the ideal soundtrack for a pretty but incomprehensible art film that no one will ever make.

This is to say, Tortoise never intended to reinvent the wheel, just have fun spinning it 'round in the studio. Sometimes the results were brilliant--"Djed" from "Millions Now Living Will Never Die" (1996) remains their "21st Century Schizoid Man" or "Close to the Edge"--and sometimes they evoked that annoying hipster Muzak that they play in the lobbies and elevators of W hotels. And the group's sixth proper album and first release in five years does not depart from that mix.

On the plus side are some of the proggiest pieces Tortoise ever has recorded: There are moments during "Prepare Your Coffin," "Penumbra" and "Minors" when you could swear Keith Emerson himself was twirling the knobs of that vintage Moog synthesizer (though it most likely was drummer and Soma Studio owner John McEntire). On the other hand, there are several tunes you could swear you've heard before--isn't "The Fall of Seven Diamonds Plus One" this band's ninth or tenth Ennio Morricone homage?--and several otherwise promising tracks, including the opening "High Class Slim Came Floatin' In," are needlessly interrupted mid-trance with pointless stylistic detours seemingly designed only to underscore that wow, these guys sure can mix it up. (It's ambient techno! No, it's ironic jazz fusion! Wait, wait, I know--that's cumbia!)

As always, how much all this appeals to you will depend on how much you like spooling that imaginary movie in your head--or how much you enjoy staying at the W.