Pushing eclecticism to its limits, Manhattan's Knitting Factory mines cover material from an unlikely source: Fiddler on the Roof. And it works: The musical's energetic ethnicity yields more than a few nuggets. Pop terrorists Negativland turn ''Tevye's Dream'' into a trippy sound pastiche; Jill Sobule's reworking of ''Sunrise, Sunset'' is appropriately understated; and the Hasidic New Wavers put a sweaty exuberance into ''Wedding Celebration.'' B

