In his introduction to Summertime, Richard Crawford wonders why there should be shelf-space for another George Gershwin biography. The book he authored doesn’t really answer the question but is written with liveliness and appreciation for the composer of Porgy and Bess and Rhapsody in Blue. A University of Michigan musicology professor, Crawford explicates Gershwin’s melodies with ease and understanding and identifies the composer’s unique sources. Gershwin was a rarity: A Tin Pan Alley songwriter who studied classical music under a Milwaukeean, Charles Hambitzer, Gershwin absorbed “the scramble, excitement and present-mindedness” of popular music alongside “the formality and timelessness of the concert hall.” Blue notes filtered through the urbane sensibility of New York’s jazz clubs (even if Gershwin never fully appreciated the black roots). Gershwin was also rare for simultaneously dominating Hollywood scores, Broadway, the pop charts and the classical concert hall, dying suddenly and young but leaving a legacy of standards.