Excellent stuff, Gibb.
Today I received an email from 'Billy Weekes' who is lurking. He tells me that somewhere in the thread you have assumed that the Chatham Theatre is in London (where Wallack performed his theatrical chanty). NYC stands for New York City. Although he was claiming to be an ex RN lieutenant he was performing in New York and actually managed this theatre.

Like many aspects of traditional music where cross-overs occur from one genre to another, or one place to another, the traffic is almost always a 2-way affair if not equally so.