Porcupine Tree fans should know by now to expect the unexpected. On the strengths of their hard rock single "Shallow" from 2005's Deadwing, the group only went on to release the excellent Fear of a Blank Planet in 2007, a palate of sonic experimentation with not a "single" to be found, as if in response to their cred-diminishing act of having scratched the radio waves. It only makes sense after such an underground masterpiece that this audacious quartet would keep the momentum chugging and delve into the heart of 1970's prog-rock.

The results of such a stroll through the history books are completely authentic, in part because Porcupine Tree has spent years forming that unique nostalgic vibe, reinventing themselves consistently since the early '90's, but also because longtime prog staple Robert Fripp (that guitar psychopath from King Crimson) was recruited to play lead on the album's title track. And if you know Robert Fripp at all, you can probably already imagine what that track sounds like: one crazy trip.

Of course, in 2008 there's not much left to do with prog that hasn't already been done. The disc plays more like an homage: there's the subtle nod to Animals era Pink Floyd in "Normal", the Eastern-tinged Tool-flavored percussion of "What Happens Now?", and a hefty helping of King Crimson throughout. But it's the perfect quilt-like blend of these influences that make Nil Recurring so thoroughly awesome. Besides, Porcupine Tree has been in the game long enough to know what works and what doesn't, and that's why there's not a second of filler to be found throughout.

With the right amount of heavy to balance out the low, the right amount of emotion to counter the mechanical time signature constructions, and of course the fact that the CD clocks in at under a half hour so it doesn't overstay its welcome like some modern prog bands we know (cough, Mars Volta), Nil Recurring is well balanced all around. It's abstractly approachable, creepily inviting, truly a rock n roll enigma.