What makes Copperfields by The Dillards notable?

'Copperfields' is significant for its innovative blend of traditional bluegrass with contemporary themes, showcasing the band's artistic growth. The album received positive reviews from critics and helped define the progressive bluegrass movement during the early '70s. Released in 1970, 'Copperfields' was The Dillards' fourth album, following their 1968 breakthrough, 'Wheatstraw Suite.' At this point, the band was solidifying their influence in the bluegrass genre while experimenting with a more eclectic sound that incorporated elements of folk and rock.