When the Grails released the compendium of their Black Tar Prophecies EPs in a single-CD volume -- two had previously been issued on vinyl only, the third was released only as part of the collection -- they found themselves exploring new and varied sonic territory. They moved away from the early post-rock schematics that had landed them in a seemingly inescapable sonic furrow. Black Tar Prophecies was their strongest recording to date. Hot on its heels, just months later, comes this behemoth of swirling, free-floating, mysterious psychedelia but it certainly doesn't end there. Elements of Eastern modal folk music, improvisational and African polyrythms, ambient soundscapes and layered textures of various "other" instruments such as guest Dylan Rice-Leary's harmonica, Cory Gray's baritone horn, and Kate O'Brien's violin add to the free-for-all while the Grails contribute enough of their own strangeness. Skin man and main keyboardist Emil Amos (who worked with Jandek as a drummer for a minute and became half of the Om duo) also plays melodica, guitarist Zak Riles -- who is part of M. Ward's band as well -- plays oud, banjo and pedal steel, bassist William Slater also plays keys (Rhodes, harpsichord), and guitarist Alex J. Hall does all the sampling. While the opener "Soft Temple" begins in a subtle enough way with throbbing bass and deep, hollow sounding drums to go along with variously stringed things, it slides into a rather minor-key slither and drone underscored by a piano playing spare lines as a "melody" though it's all mode.
It's dreamy in a rather sinister way, but drifts and moves along nicely, especially as the electric guitars enter, though they never approach din, preferring to allow the drones and Indian raga melodies speak for themselves until they reach psych mass. By "Silk Road," the third of these eight cuts, folk forms not only underscore the proceedings but inform them directly and are eventually injected with freak-outs that never quite overwhelm their rather loosely attenuated forms. Dynamics, texture and plenty of echo frame these proceedings. Melodies begin to assert themselves from the gloom only to morph into others, even more skeletal. Percussion drops in and leaves unannounced, though because of the employments of very distinctive drones, they never seem out of place and can ratchet up tempo as well as bring it down to a crawl in a very short time. There are so many change sin this piece it feels impossible to document them all. Yet the listener is never overcome by the shifts and maze-like constructs. They all seem to float, dive, dip and rise again almost effortlessly. The rest of this album moves the same way; whether it's in the truly sinister organic breakbeat workout of "Outer Banks" adorned simply by effects and electric guitars and bass, the acoustic-mass steel orgy that is "Dead Vine Blues," the space-time anachronistic dub-float meets Morricone that is "Origin-Ing," or the turtle walking, creepy crawl bliss of the title track which closes the set. If anything, Burning Off Impurities is a recording that takes on different aspects each time it is played. The Grails are their own frontier now, and have advanced the instrumental rock genre by miles, creating possibility, beauty and atmosphere everywhere they travel, but leaving beautiful ruins in their wake. One of the best bets of 2007 without doubt.