Probably referring to observations from the 1850s, in SOCIAL RELATIONS IN OUR SOUTHERN STATES (1860), D.R. Hundley writes:

No matter where they may be or what they may be doing, indeed, whether alone or in crowds, at work or at play, ploughing through the steaming maize in the sultry heats of June, or bared to the waist and with deft hand mowing down the yellow grain, or trudging homeward in the dusky twilight after the day's work is done—always and every where they are singing and happy, happy in being free from all mental cares or troubles, and singing heartily and naturally as the birds sing, which toil not nor do spin. Their songs are usually wild and indescribable, seeming to be mere snatches of song rather than any long continuous effort, but with an often recurring chorus, in which all join with a depth and clearness of lungs truly wonderfuL No man can listen to them, be his ear ever so cultivated, particularly to their corn-husking songs, when the night is still and the singers some distance off, without being very pleasantly entertained. But the wildest and most striking negro song we think we ever listened to, we heard while on board an Alabama river steamboat. We were steaming up from Mobile on a lovely day in the early winter, and came in sight of Montgomery just as the heavens were all a-glow with the last crimson splendors of the setting sun, and while the still shadows of evening seemed already to be stealing with noiseless tread along the hollows in the steep riverbanks, creeping slowly thence with invisible footsteps over the placid surface of the stream itself. A lovelier day or a more bewitching hour could not well be imagined. As we began to near the wharf, the negro boatmen collected in a squad on the bow of the boat, and one dusky fellow, twirling his wool hat above his head, took the lead in singing, improvising as he sang, all except the chorus, in which the whole crew joined with enthusiasm. And O Madame Jenny Goldschmidt, and Mademoiselle Piccolomini! we defy you both to produce, with the aid of many orchestras, a more soulstirring strain of melody than did those simple Africans then and there ! The scene is all before us now—the purple-tinted clouds overhead—the dim shadows treading noiselessly in the distance—the gleaming dome of the State Capitol and the church-spires of Montgomery —the almost perfect stillness of the hour, broken only by the puff, puff of the engine and the wild music of the dusky boatmen—and above all, the plump, well-defined outlines of some sable Sally, who stood on the highest red cliff near the landing-place, and, with joy in her heart and a tear in her eye no doubt, (we hadn't any opera-glass with us,) waved a flaming bandanna with every demonstration of rejoicing at the return of her dusky lover, whom we took to be our sooty improvisatore, from the glow which mantled his honest countenance, and the fervor with which he twirled his old wool hat in response to the fair one's signal.

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