Addendum:

The "one reference" I mentioned in the last post, to cotton-screwers of Galveston singing chanties, came from a statement by Maud Cuney Hare, the daughter of the activist/businessman/politician Norris Cuney who had organized Black screwmen. So she must have been thinking of those let couple decades of cotton-screwing—her remarks come in 1924-ish. An excerpt:

Negro chanteys were sung by the crews of the West Indian vessels that loaded and unloaded at the wharves in Baltimore. Many of the old songs are those of the longshoremen who were employed on the wharves in southern ports to stow cotton in the holds of the ships. The custom still prevails of employing large gangs of both American and West Indian Negroes in the ports of Galveston and New Orleans.

[from _The Crisis_ vol 29, #?]

Cuney-Hare, a conservatory trained musician, would go on to write _Negro Musicians and their music_ (1936).

A curiosity is this letter from her to W.E.B. DuBois, editor of _The Crisis_, asking if he'd be interested in her writing an article for the magazine on "Songs of the sailor -- those of Negro origin."
letter to Du Bois, Nov. 1924

The passage above was simply quoted in The Crisis from Cuney-Hare's piece she mentions in The Christain Science Monitor. It may be that DuBois never took interest in a chanties article, and instead just borrowed the passage after reading this letter.