Carmichael wrote the melody, based on a Bix Beiderbecke cornet improvisation, as "Bix Licks", for a project to turn the novel Young Man With a Horn into a Broadway musical. After that project failed, Carmichael brought in Johnny Mercer to write lyrics for the song.
Carmichael created the melody, drawing from Bix Beiderbecke's improvisation, and initially titled it "Bix Licks", as part of an attempt to develop Young Man With a Horn into a Broadway production. Subsequently, Carmichael partnered with Johnny Mercer to write lyrics for the song.