African-American scholars from Fisk University and the Library of Congress conducted a study in 1941-42 on the culture and music of the black community of the Mississippi Delta. Long thought to have been lost, this study has been recovered and includes 160 song transcriptions. (Music)
Just a deep, amazing read about black life and livelihood in the Mississippi River delta region from the taming of the river to the mechanization of plantation work and urban influence in the region. The bits about early blues -- delta blues -- are captivating. You're not going to find work (pun intended) closer to the source on this.