Nearing 40 and nearly broke, ousted from his last job as an English professor, a folklore buff named Robert Winslow Gordon set out in the spring of 1926 from his temporary home on the Georgia seacoast, lugging a hand-cranked cylinder recorder and searching for songs in the nearby black hamlets.

One particular day, Mr. Gordon captured the sound of someone identified only as H. Wylie, singing a lilting, swaying spiritual in the key of A. The lyrics told of people in despair and in trouble, calling on heaven for help, and beseeching God in the refrain, “Come by here.”

With that wax cylinder, the oldest known recording of a spiritual titled for its recurring plea, Mr. Gordon set into motion a strange and revealing process of cultural appropriation, popularization and desecration. “Come By Here,” a song deeply rooted in black Christianity’s vision of a God who intercedes to deliver both solace and justice, by the 1960s became the pallid pop-folk sing-along “Kumbaya.” And “Kumbaya,” in turn, has lately been transformed into snarky shorthand for ridiculing a certain kind of idealism, a quest for common ground....