“Summertime” is an aria composed by George Gershwin for the 1935 opera Porgy and Bess. The lyrics are by DuBose Heyward, the author of the novel Porgy on which the opera was based, although the song is also co-credited to Ira Gershwin by ASCAP. There are over 25,000 recordings of “Summertime”. In September 1936, a recording by Billie Holiday was the first to hit the US pop charts, reaching #12.  I sing both the traditional version as performed by Sarah Vaughan and the updated jazz version by Eva Cassidy.
Sarah Vaughan’s Traditional Version

Summertime by Sarah Vaughan on YouTube