Please answer a question about the following article about Charleston, South Carolina:

As many as five bands were on tour during the 1920s. The Jenkins Orphanage Band played in the inaugural parades of Presidents Theodore Roosevelt and William Taft and toured the USA and Europe. The band also played on Broadway for the play "Porgy" by DuBose and Dorothy Heyward, a stage version of their novel of the same title. The story was based in Charleston and featured the Gullah community. The Heywards insisted on hiring the real Jenkins Orphanage Band to portray themselves on stage. Only a few years later, DuBose Heyward collaborated with George and Ira Gershwin to turn his novel into the now famous opera, Porgy and Bess (so named so as to distinguish it from the play). George Gershwin and Heyward spent the summer of 1934 at Folly Beach outside of Charleston writing this "folk opera", as Gershwin called it. Porgy and Bess is considered the Great American Opera[citation needed] and is widely performed.

What was the name of the "folk opera" based on 'Porgy'?
Porgy and Bess