GARRISON KEILLOR is host of ``An American Christmas in Copenhagen,'' airing Saturday from 8 to 9:30 p.m. (Eastern time) on the American Public Radio network. The former ``Prairie Home Companion'' host will take a walking tour of Copenhagen and reflect on Christmas in a series of short monologues. The program includes Danish carols and a visit to the home of a Copenhagen family. THE EMERSON QUARTET has announced that the current season will mark the end of its residency at the Chamber Music Society of Lincoln Center. This and other resignations (which include mezzo-soprano Frederica von Stade) are part of incoming music director Fred Sherry's plans to overhaul the society. CHRISTMAS MUSIC RINGS OUT in Boston Saturday, as the Boston Pops kicks off a series of Symphony Hall concerts under the direction of John Williams, Harry Ellis Dickson, and Ronald Feldman, and the Boston Camerata, an early-music ensemble, presents ``A French Christmas'' at the New England Conservatory's Jordan Hall. The Pops program will feature music by Tchaikovsky, Handel, Kod'aly, and Alfred Burt. The Camerata program, conducted by Joel Cohen, includes medieval chants, songs from the French-speaking court in Cyprus, motets from the King's Choir at Ste. Chapelle, and 16th-century Renaissance dances and carols. `THE WIZARD OF OZ' has been adapted for the Radio City Music Hall stage by Michel M. Grilikhes. The production is set to premi`ere March 22 and run through April 9, before embarking on a national tour.