Your hackles may raise at the sight of Darol Anger or Mike Marshall"s name in the context of country or folk music, but as avatars of an indefinable genre--call it "jazzgrass"--they"ve taken fiddle, mandolin, and guitar into some shockingly imaginative places, even if the results can sometimes be more intriguing as theory than as music. The two former David Grisman sidemen may claim to be making "stringband music for the next millennium," but this collaboration jettisons traditional structures completely, while still finding some shockingly beat-savvy textures--courtesy of Derek Jones"s moaning fretless bass and Aaron Johnston"s half-rock/half-jazz drumming--as well as some luxuriant, Eastern-based melodies, especially the opening "Couscous" and the final group improvisation (of three) "Autumn Aleatorics." The eclectic influences can be measured in the cover choices--Hendrix, Bach, and Brazilian mandolinist Jacob Do Bandolim--and the overall approach is that of world music shot through with heady, challenging improvisation. Jam is the funkiest, earthiest album Anger and Marshall have made to date. --Roy Kasten