To mark their 50th anniversary, the versatile King’s Singers returned home to King’s College, Cambridge, for a program spanning the entire history of Christmas music. It stretches from the perennial beauty of early plainsong to former King’s Singer Bob Chilcott’s magical “A Thanksgiving,” featuring the National Youth Choir of Great Britain. These two divine works frame sprightly Sweelinck, luscious Herbert Howells, and suave and swaggering Poulenc. The final quarter of this recording features touching arrangements of traditional and popular works, plus the delightful, moving “La Peregrinaçion.”