>On PBS, Great Performances brings us two giants of popular music. Music by Richard Rodgers, a tribute to the prolific composer of so many of our best-loved melodies, airs Friday (March 16, 9 P.M. ET). What makes it so hugely entertaining is the cavalcade of clips from the scores of Broadway and Hollywood productions on which Rodgers collaborated, lingering lovingly over the Hammerstein era. On Sunday (March 18, 9 P.M. ET) there’s Julie Andrews in Concert, a beefed-up version of the one-woman song-and-spiel show she recently took on tour. Andrews reprises her glorious career from a child in British vaudeville to music theater to film stardom.