Classical Debussy, Calude: "La Mer." "Trois Noctumes." Tanglewood Festival Chorus. Boston Symphony Orchestra, Sir Colin Davis, conductor. (Philips digital 6514260) -- The tradition of the Boston symphony and Debussy continues. from the days of Koussevitsky, through Monteux, Much, Abbado, and Thoas, distinguished Debussy albums have been a regular part of the orchestra's output. This "La Mer" boasts gorgeous sound, and performaces that are occasionally startlin in their insights , but too regularly a bit prosaic, unatmos;heric, even plodding. "La Mer" fares better than the "Nocturnes." In the latter group, "Fetes" is particularly four-square, through "Sirenes" manages to haunt and here Davis is at his very best.