While the Grand Ole Opry—which both preceded it and continues into the present day—is better known, the Louisiana Hayride, broadcast from Shreveport in that state from 1948-60, has earned an indisputably vital place in the history of country music. Unlike the Opry, the Hayride demonstrated a willingness to showcase up-and-coming talent, like a kid from Tupelo with the odd name Elvis, who first appeared on the radio program in 1954 and then returned a year later for the Hayride’s television version. Presley sang 15 songs in all during his visits, all of them included on this massive boxed set from the German Bear Family label. How massive? There are 20 CDs in the nine-pound box, featuring more than 500 songs in all, by 167 artists—that’s more than 24 hours worth of music. A visually stunning and highly informative 200-plus-page hardcover book also comes with the set. Beside Elvis, the most familiar names whose rare music can be heard include Hank Williams, Johnny Cash, Kitty Wells and George Jones, but some of the most rewarding surprises come from those who never made a dent on the national scale and those who did make it big but whose entries reveal a different side: pre-success Roger Miller’s “Your House Is Not a Home,” Loretta Lynn’s “Mind Your Own Business” and many more. June Carter rocks Chuck Berry’s “30 Days,” Cajuns Rusty and Doug Kershaw display a pop side on “Dancing Shoes” and Johnny Horton reveals himself to be a forerunner of the Americana movement with songs like “John Henry” and “Johnny Reb.” A collection this bountiful is best absorbed, perhaps, in smallish doses, but no fan of vintage country music will want to pass on this essential document.