Leonard was born in Kansas City in 1905. A professional musician from the age of 17, he joined Bennie Moten's orchestra in 1923, where he led the reed section until 1931.
In 1931, he and Thamon Hayes formed the Kansas City Skyrockets, which included trumpeters Ed Lewis and James Ross, trombonist Vic Dickenson, and pianist Jesse Stone. After disputes with the Chicago local of the American Federation of Musicians the band broke up.