After the pan-stylistic moves of the Silk Road Ensemble, an album of beloved pieces for cello and piano might seem like Yo-Yo Ma’s retreat into traditionalism. But his program with pianist Kathryn Stott includes surprises between two versions of “Ave Maria.” (The Bach/Gounod item opens; Schubert’s closes.) Messiaen’s “Louange à l'Éternité de Jésus” is not often heard near Brahms’ “Lullaby,” but this duo’s warm compatibility is present at every turn. And their concept, regarding works that make up the “soundtrack” of a life, holds together beautifully.