Last night, NBC mounted a live production of The Sound of Music. Monday, HBO is presenting a new biographical and music-filled tribute to Stephen Sondheim. And tonight, to keep that musical theater ball rolling, MGM HD – one of the best places to watch this kind of ultra-widescreen presentation – is televising the 1961 movie version of West Side Story, with music by Leonard Bernstein and lyrics by Sondheim. Natalie Wood stars.