What was the name of the opera which You Send Me and Summertime were both songs on the album?
You Send Me:  Produced by Bumps Blackwell and arranged and conducted by René Hall, the song was the A-side to "Summertime". Summertime (George Gershwin song): "Summertime" is an aria composed in 1934 by George Gershwin for the 1935 opera "Porgy and Bess".
Porgy and Bess