Yo-Yo Ma's new CD “Songs of Joy and Peace” centers around "Dona Nobis Pacem (Give Us Peace)," on which the cellist and various friends improvise every few tracks. Between these markers there’s fiddler Natalie MacMaster performing "Tobique Reel," Diana Krall in "You Couldn’t be Cuter," Paquito D'Rivera doing "The Christmas Song," and Dave Brubeck in "Joy to the World," among others.