With its bold new brand of acoustic music, Joy Kills Sorrow pushes right through the envelope and out the other side. The Boston-based stringband brings a decidedly modern sensibility to an old-world sound, channeling the prodigious talents of its individual members into elegant arrangements and well-crafted songs. While the group pays due homage to its Bluegrass roots—its name is taken from WJKS, a radio station that broadcasted the Monroe brothers’ show in the 1930s—the band truly excels in its rich and textured treatment of more contemporary material. Boasting a full arsenal of original songs, Joy Kills Sorrow plumbs the entire spectrum of its spare instrumentation, effortlessly merging influences as diverse as folk, rock, pop, and jazz. The music that emerges is dark and often funny, ruminating on modern life and love with eloquence and wit. The result is a radical new strain of folk music, one that bravely breaks with tradition even as it salutes the past.