This is from a historically interesting essay by Judge George N. Aldredge of Dallas, “Plantation Life in the Old South," in the Dallas Morning News (Oct. 30, 1898). It refers explicitly to the 1850s.

Aldredge was born in 1846 and joined the Confederate army as a private when he was 16. After the war he became prominent as Dallas County Attorney and then Judge of the Eleventh Judicial District. He was later a nationally known speaker on the subject of the gold standard.

Besides the earliest known mention of "Cotton-Eyed Joe," Aldredge's essay includes a positive description of antebellum folk tunes played by African Americans. Though conventionally patronizing of black people, Aldredge wrote that "slavery was contrary to the genius of America." More to the point here, he implicitly recognized the ability of music to pass across class and racial barriers even before the Civil War:

“There was plenty of laughter and song throughout the [slave] quarters every night, but Saturday night was the gala event of the week. Then the banjo and fiddle were brought forth and erratic feet, to perfect time, chased the glowing hours. On such occasions they were all there. No amount of ‘piousness’ could hold a negro away when ‘Cotton-eyed Joe’ and ‘Mollie, Put the Kettle On’ enriched the air. The banjo and fiddle were accompanied by a negro who could ‘pat’ in a marvelous manner. Any true southern boy would have turned away from any grand opera or brass band to listen to such a trio. Its drawing power often reached the ‘big house.’ Many a time, when I was a boy, has my father run me out of the cabin late at night, where I was assiduously delving into the mysteries of the back-step and double-shuffle, or learning to ‘cut the pigeon wing.’”