The Windham Hill label was the '80s Norah Jones an easy-listening brand that wafted through every bookshop in America. But despite derision and sketchy '90s output, the beauty of their best acoustic instrumental releases remains undeniable. A Quiet Revolution: 30 Years of Windham Hill, an uneven four-CD retrospective, is essentially a buyer's guide to discs by George Winston, Will Ackerman, Michael Hedges, and others whose ''background music'' merits full attention.

