Hi Mike,
Yes I agree the impact of the minstrel stuff from about 1844 onwards is dramatic. They were the Beatles songs of their day and had enormous influence both at sea and on land.

Gibb,
Am in complete agreement on the later arrival of halyard shanties.

'Round the Corner Sally' comes from the minstrel influence. Lady of easy virtue. see Hugill p389. Its use as a reference to Cape Horn, if ever used in that way, probably came later.

Charley, what evidence is there to suggest that the cook's song was a shanty?