The original key of the song "Summertime" by George Gershwin is D minor. It was composed as part of the opera "Porgy and Bess" in 1935. The song has been interpreted by numerous artists over the years, including Billie Holiday, Ella Fitzgerald, and Janis Joplin. A curious fact about the song is that the lyrics were written by DuBose Heyward, who also wrote the novel on which the opera is based. The melody of "Summertime" is known for its haunting and evocative nature, with a slow tempo and beautiful melodic lines.