For a record that seemed like a high-concept joke, Danger Mouse's The Grey Album has developed into serious business. As you may have heard, Danger Mouse -- a.k.a. underground hip-hop producer Brian Burton -- wiped away the backing tracks from Jay-Z's ''The Black Album'' and replaced them with beats and textures created from snippets of The Beatles, famously known as ''The White Album'' (hence the new work's nyuck-nyuck title). In liner notes of early copies that began circulating in stores and on the Web, Mouse dubbed it ''an art project/experiment I did that I thought some people might like.'' Among those who didn't like it very much were EMI, the Beatles' corporate parent, which issued cease-and-desist orders to anyone distributing the disc. In protest, hundreds of websites offered free downloads of the album on ''Grey Tuesday,'' Feb. 24, making the homemade disc the most talked-about, and probably listened-to, underground recording of all time.
Legally, ''The Grey Album'' shouldn't have happened without sample clearance. (Anyone who thinks EMI wouldn't have cared is naive.) Artistically, it shouldn't have even worked, since the merging of Jay-Z and Lennon-McCartney is essentially a mash-up -- the played-out vogue of melding, Frankenstein-style, the vocal from one song and the instrumental backup from another.
But concerns about authorization and logic fall by the wayside as soon as one actually hears ''The Grey Album,'' a startlingly, shockingly wonderful piece of pop art. Although musicians have been fusing rap and classic rock for decades, few have approached it with Danger Mouse's ingenuity and imagination. The producer took familiar ''White Album'' motifs -- the strums from ''Rocky Raccoon,'' the harpsichord from ''Piggies,'' the gentle guitar figure from ''Julia'' -- and looped them, lending Jay-Z's music a radiant new sparkle. Metallic shards of ''Glass Onion'' guitar slice through a newly propulsive ''Encore,'' replacing Kanye West's old-school-homage production; ''99 Problems'' now rattles just as effectively to the riff from ''Helter Skelter,'' rather than the original's Mountain and Billy Squier samples.
At the same time, ''The Grey Album'' works on more than a name-that-hook level. The grafting of the dramatic piano from ''While My Guitar Gently Weeps'' onto ''What More Can I Say'' gives Jay-Z's admissions of his hustle-driven career an added tension and grandeur. The use of ''Mother Nature's Son'' as a new raison d'etre for ''December 4th'' isn't just appropriate -- both tunes are about growing up -- but witty. ''Public Service Announcement,'' ''The Black Album'''s second interlude, replaces the original's taut beats with the floaty sounds of ''Long, Long, Long,'' resulting in a sort of hip-hop techno-folk. In a strange way, ''The Grey Album'' hangs together better than ''The Black Album,'' since the latter's slew of producers and styles -- from the Neptunes' R&B slink to Eminem's brooding symphonic hip-hop to Timbaland's familiar dots-and-dashes approach -- made for a patchwork end result.
Danger Mouse's ''Black Album'' remixes aren't the first and maybe not even the best -- one website lists nearly a dozen other illicit Jay-Z DJ mix discs. But it's an exemplary example of the form, not to mention a legal flashpoint: If Danger Mouse didn't intend to officially release it and wasn't actually selling it, does EMI have sufficient grounds to clamp down on its availability? But in the way it draws a connection between two very different eras of pop rebellion and artistry, ''The Grey Album'' raises a far more important question: Shouldn't bad rap-rock, of the limpbizkit variety, be illegal instead?