Within the discount, ugly-duckling packaging of The Real Music Box: 25 Years of Rounder Records lie nine CD swans worth several hundred times their weight in superficial music-industry gold records. Since 1970, Massachusetts-based Rounder has been a stalwart sanctuary of various musics at the root of what has recently been labeled "Americana." The retrospective is segmented into four thematic two-disc sets, each offering a staggering 30 to 50 tracks where legendary names rub shoulders with bright young Rounder talent.