By 1965, ' star shone so brightly that even -- the biggest band the world had ever known -- wanted to follow in his footsteps, covering his hit single on their album, thereby kick-starting the golden era of country-rock in the late '60s. Thanks to , many young rock & rollers now turned to 's Bakersfield sound as their template for what country music should be, reinvigorating rock & roll by adding what they learned from country, essentially reversing the equation came up with at the start of the '60s, when he applied everything he learned from rock & roll to create the signature sound of that decade. was grounded in '50s country but he had his head turned by rock & roll, eventually threading in the driving backbeat and electric guitars to his honky tonk background. This sound -- lean yet powerful as a locomotive, all fueled by the twin guitars and harmonies of and his right-hand man, -- became known as the Bakersfield sound, and it dominated country in the '60s, ruling the charts while creating scores of imitators and acolytes from to and . The creation of that sound has never been as well documented as it is on 's 2008 set , which runs five discs and 159 tracks. Sometimes these big sets are heavy on unreleased tracks, but that's not the case here; only 16 of the 159 cuts are previously unreleased (with 13 of them being alternates tacked onto the end of the set). This set may be skimpy on unreleased music, but most of 's recordings have been in circulation on CD, as licensed his LPs to for reissue (making him one of the few major country artists to have almost all his proper LPs appear on CD) and his pre- recordings were nearly all rounded up on 's 2001 set, . So, the value of -- as it is with almost any set -- is context, provided both by 's excellent hardcover biography and the presentation of the music itself as the set systematically marches from his early recordings for to his big hits for . What's startling about this is that those early singles do reveal 's roots so clearly, whether it's the debt has to or how has the unmistakable midtempo gait of 's later or how the rockabilly of -- a single released under the name -- hinted at the twanging Telecasters of his prime work. All these elements were in place from the start, but it took a while to get there and follows every one of his footsteps, from his time backing on his sessions to the first flowering of his signature sound on in 1960 through 's switch from fiddle to electric guitar roughly a few months later. As the '60s rolled on, didn't expand his Bakersfield sound so much as hone it, sanding off the edges and turning it into something cleanly efficient yet surprisingly versatile. Whether he was singing heartbreak ballads like and skipping through neo-novelties like or singing tunes by -- or turning in renditions of 's that provided the blueprint for decades of country-rock to come -- he always sounded unmistakably like himself. He had a sound like no other and, with his expert ear, he built a songbook -- partially originals, partially expertly chosen covers -- that defined what modern country music was all about in the last 40 years of the 20th century. His impact is of course well known, but nowhere is it easier to appreciate than it is on this marvelous set. ~ Stephen Thomas Erlewine