"Rock & roll" and "Eddie Cantor" are not two terms frequently heard together. But the comedian is precisely the perfect person to start off this collection of "The Secret History of Rock & Roll." RCA Victor and Bluebird have ingeniously figured out a way to present their vast treasure of historic recordings from the earliest years of the record business. The conceit that every musician that came before Elvis was merely laying groundwork is absurd. Still, hearing the gutsy jazz, blues and folk that provided musical refuge for those discontent to settle for syrupy pop is revelatory. This disc is the fifth in the series and offers a wide range of the music that kept people sane throughout the Depression. Whether it's the giddy swing of "Ten Cents a Dance" by the High Hatters lifting people's spirits or the thoughtful tales of Sonny Boy Williamson and Woody Guthrie providing commiseration, the deep impact of the economy's collapse was inescapable. The two dozen cuts are crazily diverse -- blues, folk, jazz, gospel, bluegrass, vocals -- scuttling any misconception folks might have about the era's monochromatic sound. So, what does Eddie Cantor have to do with rock & roll? Not much, but he had a lot to do with providing popular entertainment during the era, and, like the distractions of today, that's as essential as it gets.