Box sets frequently do a disservice to artists and audiences alike. Few acts can support a four-disc collection, and the catalogs of those who can are often worth owning in their entirety. By an almost desperate necessity, most collections fill space with rare or unreleased, generally weak material that dissipates the quality of the sets' best music. El Cancionero: Mas Y Mas, a new Los Lobos collection that features most of the tracks from the band's previous two-disc anthology plus several dozen more, bucks the odds, but who would expect anything less from L.A.'s rock 'n' roll legend? Now about 25 years into their recording career, the members of Los Lobos (David Hidalgo, Steve Berlin, Conrad Lozano, Louie Pérez, and Cesar Rosas) continue to challenge themselves, exploring strange side projects and contributing to film soundtracks, but they always return to each other. Because Los Lobos works so well on every front, the box-set format for once makes sense: After recording an impressive string of strong albums and constantly touring in each interim, the band amassed more than enough material to make El Cancionero a thrill from start to finish. The box collects key album tracks and the usual live recordings, rarities, and alternate versions, but it also compiles valuable songs from varied solo projects and soundtracks, ensuring that no gaps remain. The chronological set begins with songs from Los Lobos' slightly more traditional early start, featuring sad norteños and rockabilly numbers drawn from hard-to-find early releases such as …And A Time To Dance and the recently reissued Del Este De Los Angeles. Subsequently, the band's output coincided with the L.A. roots-rock revival (as with songs from the 1984 breakthrough How Will The Wolf Survive?) through its commercial peak (from the 1987 La Bamba soundtrack), and finally to the adventurous anything-goes period that resulted in modern masterpieces like 1992's Kiko and 1996's Colossal Head. The set strews covers of acts as varied as The Grateful Dead ("Bertha"), James Brown ("Try Me"), and The Beatles (a stunning live "Tomorrow Never Knows"), lest anyone doubt the group's all-encompassing scope. To Los Lobos' credit, it never loses touch with its Mexican roots, offering plenty of Spanish-language tracks that sound just as seamless as the rock 'n' roll material. Of course, the usual box-set standard still applies, and each of Los Lobos' albums do stand up in their own right. But so does El Cancionero, a remarkable encapsulation of a constantly moving career that would seem resistant to such convenient canonization.