CHANTS DE L'EXILE: JEWISH MUSICIANS IN EXILE, 1200-1600 A.D. Boston Camerata, Joel Cohen, director. Erato Records STU 71429. The value of such a collection of Jewish music to the scholar of European history is incalculable, but for the average listener the record will likely be dull. The opening Gregorian chant may numb the most zealous music lover. The beat of the song "Par Grant Franchise" and the drone of "Wa heb' uf" quickly wear away their welcome. And the proliferation of French on the album jacket may discourage those not versed in that language.