Harold Arlen was an American composer of popular music, having written over 500 songs, a number of which have become known worldwide. In addition to composing the songs for The Wizard of Oz, including the classic 1938 song, "Over the Rainbow,â Arlen is a highly regarded contributor to the Great American Songbook. "Over the Rainbow" was voted the twentieth century's No. 1 song by the Recording Industry Association of America and the National Endowment for the Arts .