At the County Museum a couple of weeks before, that precious series known as the Monday Evening Concerts also began with Copland, with performers from the Copland House -- the composer‘s home in the Hudson Valley, now maintained as a study center -- in an elegant program of chamber music including the Piano Quartet, most successful of the “atonal” works, and the searing Vitebsk Trio, a tribute to its creator’s ancestry. Pianist Michael Boriskin and flutist Paul Lustig Dunkel, the center‘s co-directors, were among the players, obviously collaborating in a labor of love, in music that deserved no less.