While Blow and Purcell were making high art in Britain, a rich folk culture of Anglo-American music was developing in New England and the South - as "Come to the River: An Early American Gathering," a new release by the excellent Cleveland group Apollo's Fire (on Avie) makes delightfully clear. Jeannette Sorrell, the ensemble's harpsichordist and director, has done most of the arrangements on the album, short vocal and instrumental pieces that have origins in material collected by the seventeenth-century English musician Thomas Ravenscroft ("Willie, Prithee Goe to Bed"), the Sacred Harp tradition of shape-note singing, or the work of anonymous American balladeers ("Wild Bill Jones"). The disk is evidence of a maturation of "crossover," in which early music and folk performers are joining forces to make a new kind of sound.