Few composers conscientiously write “final” music. Schubert’s “Swan Songs” collection was assembled and titled by a savvy publisher. Contrary to a popular rumor, Mozart probably didn’t really think he was writing a requiem for himself. Likewise, Strauss’s beautiful “Four Last Songs” were given their titles for a posthumous premiere performance following the composer’s death. The song we just heard was Strauss’s very last completed work, finished, ironically, in September of 1948. Strauss completed the last song in the cycle, “At Sunset,” about two years earlier. The text, by 20th-century German writer Herman Hesse, meditates on the changing of the seasons and the yearning for rest and peace.