The alchemists of Yes melded musical elements into the first formulas for progressive rock, sonic concoctions that stood apart from the flower-fueled pop of the late '60s. In the band's first year, Yes opened for Janis Joplin and signed to Atlantic Records for its eponymous 1969 debut. The platter combined precise rhythms, piercing twofold guitar riffs and intricate keyboard work with singer Jon Anderson's definitive, aerial vocals and comparatively unpolished production. Before Yes released its second album, the band was rocked by internal dissension, and one original member left -- but the music's academic construction and inventive approach continued to draw fans. Subsequent albums delivered skillful arrangements on tracks dominated by swooping chords and evocative melodies, with extensive solos inside mystical atmospheres. And then came 1983's 90125. Named for its catalogue number, the disc deviated from earlier patterns and delivered a straight-ahead rock-and-roll record free of orchestral instrumentation and lofty ambitions -- but with one big, number-one single, "Owner of a Lonely Heart." 90125 also netted the group its only Grammy. Disciples of the legendary band -- as well as enthusiastic novices -- can say yes to Yes twice this weekend, when the group affirms its timeless authority at Red Rocks Amphitheatre on Friday, September 10, followed by a show September 11 at the Budweiser Events Center -- both times with fellow prog-rock performers Dream Theater.