Before Dylan and that crucial British invasion (circa 1964), instrumental rock 'n' roll was not a specific subgenre. Its executors, however, actually topped the charts — the Ventures, Dick Dale, and Link Wray sold millions of records, influencing dozens of 1960s and '70s guitarists. Although instrumental bands still exist, many have retro leanings (such as Los Straightjackets) — not that there's anything wrong with that. Portland's Grails, however, do not. While Burning's compositions have a high catchiness factor on a par with the Ventures, Grails is more influenced by the less hokey aspects of psychedelic rock along with world music — specifically motifs and scales from India and the Middle East — adding just a smidgen of metal to the mix. "Silk Rd." is somber yet compelling belly-dance music from Haight Street '67, and "Outer Banks" flickers like rainwater landing on hot pavement, adding a dab of spacious dub when needed. "Dead Vine Blues" features sparkling, John Fahey-like, acoustic guitar picking against a gentle, cavernous roar (recalling Calexico at its most Sergio Leone-like). Dense and enigmatic sans pretentiousness, Burning Off Impurities is serious fun.