According to Wikipedia there are more than 33,000 covers of Summertime. Any version by Ella Fitzgerald is the finest. This one, from German TV in 1968, is my favorite. Though the sound quality of the minimal instrumentation is poor, her voice is magical and haunting, almost as though she is reciting a prayer. Her ability to control tone throughout her register is remarkable.
The music for the song was composed by George Gershwin (who also co-wrote, with brother Ira, several of the songs introduced by Fred Astaire and Ginger Rogers). The lyrics are by Dubose Heyward. Heyward, born in 1885 in Charleston SC, descendant of a signer of the Declaration of Independence and of the state's planter elite, became interested in the low country black community and wrote the novel and play Porgy in the 1920s. He then teamed with Gershwin to create the opera Porgy and Bess which premiered in 1935.
Below is another of the 33,000, a casual soundcheck before a 1990 concert in Osaka, Japan by Prince and his band.