 Unbridled's Song was a gray stallion who was bred in Kentucky by Mandysland Farm.He was sired by 1990 Kentucky Derby winner Unbridled, whose other important offspring included Derby winner Grindstone, Preakness winner Red Bullet and Belmont Stakes winner Empire Maker.His dam, Trolley Song, is a winning daughter of Caro out of Lucky Spell, a stakes winner and stakes producer.