George Gershwin employed the pentatonic scale in a number of his works, most notably in the lullaby, Summertime, from the opera, Porgy and Bess. The haunting, emotional directness of Gershwin's pentatonic melody imbues Summertime with an indelible sense of loss and desire. In his song, Someone to Watch Over Me, Gershwin captures the yearning of the opening lyiric, "There's a someone that I'm longing (to see)", by painting the phrase with an unresolved ascending pentatonic scale.
As John Goldsby writes,
Once in a while, a song crosses musical boundaries and becomes a classic standard. Well written and resilient, “Summertime” has been recorded and performed countless times—by jazzers like Billie Holiday and Miles Davis, and rockers like Janis Joplin and Annie Lennox. It’s played at blues gigs, Latin gigs, jazz gigs, cabaret gigs, weddings, concerts, and jam sessions.
George Gershwin composed “Summertime” in 1934 as part of his opera Porgy and Bess. Gershwin succeeded in creating a bluesy, pentatonic-scale-based melody, echoing the sound of African-American spirituals of the day. The original operatic version is a child’s lullaby, underpinned by hip New York jazz harmony and a slow, Southern-state rocking-chair vibe.
- From George Gershwin's Summertime: Exploring a Classic by John Goldsby (Bass Player Magazine, September 15, 2015)