Since my upcoming Wolf Trap concert features four singers and two pianists, it seemed crazy not to open the program with the cornerstone work for those forces: Brahms’ Liebeslieder Waltzes. Normally I shun the obvious, so I briefly considered delving into the four-part writing of Szymanowski or Schoeck or Schreker. After about 40 seconds I came to my senses. Some pieces are evergreen, and the Liebeslieder are at the top of that last.