"In the world of sports," promises the Kentucky Derby's website, "there is not a more moving moment than when the horses step onto the track for the Kentucky Derby post parade and the band strikes up 'My Old Kentucky Home' and 160,000+ people sing along."

The tradition of playing the song on Derby Day dates back to at least 1921."Since 1936, with only a few exceptions, the song has been performed by the University of Louisville marching band as the horses make their way from the paddock to the starting gate," the Derby's official history explains.

The Derby crowd sings along — a scene captured by the TV broadcast. Many people belting out the lyrics have no idea that the history behind the song is so fraught.

"My Old Kentucky Home" is Kentucky's state song. It was written before the Civil War by Stephen Foster, who is considered the "father of American music." The song has been recorded by musicians ranging from Al Jolson and Bing Crosby to Marian Anderson and Louis Armstrong.

But last month the city of Pittsburgh, Foster's hometown, removed a statue of him with a black man sitting at his feet, singing and strumming the banjo.

The 800-pound statue, created in 1900 by Italian sculptor Giuseppe Moretti, had been a controversial monument at Schenley Plaza, with critics saying it "glorifies white appropriation of black culture, and depicts the vacantly smiling musician in a way that is at best condescending and at worst racist," the Pittsburgh Post-Gazette reported. Defenders argued that it simply showed Foster listening to a song by a black musician.

Foster is remembered for "Oh! Susanna," "Hard Times Come Again No More" and "Old Folks at Home" (or "Swanee River").

"My Old Kentucky Home" is different. It is a lament by a slave who has been sold, is bound for the Deep South and must say goodbye to his birthplace. It hints at the brutal mistreatment he faces: "The head must bow and the back will have to bend … In the field where the sugar-canes grow."

In a 2010 NPR interview, music critic Ken Emerson, who wrote a Foster biography, said "My Old Kentucky Home" was inspired by the anti-slavery novel "Uncle Tom's Cabin."

"Ironically," Emerson said, "here is a song that was inspired by a great abolitionist novel, and which no less a leader then Frederick Douglass himself singled out as a song that awakens the sympathies for the slave, in which anti-slavery principles take root and flourish. So, like all of Foster's music, it's thick with contradictions that, to this day, I think, are part of the American experience."

In 1986, the Kentucky General Assembly passed a law replacing the words "darky" and "darkies" with "people." The altered lyrics are the ones now sung at Churchill Downs.