Gustav Gerson Kahn was an American lyricist who contributed a number of songs to the Great American Songbook, including "Pretty Baby", "Ain't We Got Fun?", "Carolina in the Morning", "Toot, Toot, Tootsie ", "My Buddy" "I'll See You in My Dreams", "It Had to Be You", "Yes Sir, That's My Baby", "Love Me or Leave Me", "Makin' Whoopee", "My Baby Just Cares for Me", "I'm Through with Love", "Dream a Little Dream of Me" and "You Stepped Out of a Dream".

The Great American Songbook is the loosely defined canon of significant 20th-century American jazz standards, popular songs, and show tunes.