“An American in Paris,” “Rhapsody in Blue,” and Hancock’s improvisation on a Gershwin standard fill the bill.

View the production credits for "The Great American Songbook."

"Porgy," the opera by Gershwin, nearly became "Porgy," the musical comedy by Jerome Kern and Oscar Hammerstein II.

In 1938, TIME magazine wrote: "As Rodgers and Hart see it, what was killing music comedy was its sameness, its tameness, its eternal rhyming of June with moon."

The American movie musical transformed Hollywood into a Mecca for the biggest singing stars and leading songwriters of the '30s, '40s, and '50s.