All right, so we will let pass without further comment the strange coincidence of the holiday honoring Martin Luther King, Jr.—and all the noble ideals he stood and died for—falling this year on the same day as the inauguration of the incoming president. We shall instead focus on another profoundly decent man who also called us to our better angels over a long career of music-making. I, perhaps like you, have sung David Mallett’s music out loud on various occasions over many years now without even knowing who he was. His “Garden Song” (“Inch by inch, row by row….”) has…