-This from the IMS website-
"Although there are reports that "Indiana," as the song was originally titled when published in 1917, was played by a trackside brass band as Hoosier driver Howdy Wilcox ran out his final laps on the way to winning the 1919 "500," it was not until 1946 that it was sung on race morning. James Melton, of the New York Metropolitan Opera Company, was a collector of classic cars, and was at one time president of the Antique Automobile Club of America. He supplied several of the vehicles which participated in a race-morning lap of classic automobiles around the track in 1946, and approximately 45 minutes before the start of the race, he sang "Indiana" with the Purdue University band over the public address system. It was so well received that he was invited back the following year, and in 1948, it was decided to "move it up" to its current slot in the order of the day, just prior to the firing of the engines. Among Melton's better-known successors have been Mel Tormé, Vic Damone, Dinah Shore, Ed Ames, Peter Marshall, Dennis Morgan and Johnny Desmond, with popular Jim Nabors having missed only a handful of years since 1972."