In the 48-page booklet that accompanies the handsome, hardbound packaging of A Quiet Revolution, long-time producer Dawn Atkinson succinctly defines Windham Hill's core sound as "acoustically rooted music that is a blend of folk, classical and jazz influences." Guitarist Will Ackerman, who launched the label in 1976 with a tiny pressing of solo works, boils its essence down to a single word, adding "it's a word seldom associated with the music industry: innocence." Windham Hill rocked the music trade in the late 1970s by turning down the volume and cultivating intelligent, heart-probing, all-instrumental music that--largely through word of mouth--won over legions of fans attracted to the label's earthy vibe, elevated craftsmanship, and overriding sense of purity. Much of what gave Windham Hill its soul-stirring allure is nicely displayed in this four-disc anthology--a 67-track compilation that includes four previously unreleased live tracks (including "Because It's There" by guitarist Michael Hedges and "Clockwork" by Alex de Grassi). 　　The music on A Quiet Revolution is sorted by general style, not chronologically. Discs 1 and 2, Elements and Peace, focus more on the label's pastoral textures, and disc 3 (Artistry) explores more ambitious or ensemble pieces. Disc 4 (Excursions) might be viewed by some long-time fans as "Wayward Hill," with its assortment of latter-day vocal stylings and traces of smooth jazz. Beyond that and a few other head-scratching choices, there's much to like here, with stellar tracks from Liz Story (whose brilliant Solid Colors may be the label's finest release) to works from Ackerman, George Winston, Nightnoise, and lesser-known artists, such as guitarist W.G. Snuffy Walden and his small gem "Angela Smiled." Enlightening liner notes are by Echoes radio host John Diliberto and former Billboard writer (and past Windham Hill staffer) Sam Sutherland. For newcomers curious to know what the blissful fuss was all about a few decades ago, A Quiet Revolution provides an inviting overview. --Terry Wood.