If the mid-19th century pub was near a waterfront, a large percentage of the singers and audience were also working merchant mariners:

“I shall never forget hearing an old salt, who had broken his voice by hard drinking on shore, and bellowing from the mast-head in a hundred north-westers, with all manner of ungovernable trills and quavers – in the high notes, breaking into a rough falsetto – and in the low ones, growling along like the dying away of the boatswain's “all hands ahoy!””
[Two Years Before the Mast, Dana]

And, if that electric bass player is sporting a tri-corner hat, “shanties” is just fine. Party on dudes.

Maritime museum docents &c&c, a tad more historically accurate wardrobe/accompaniment/voice/glossary is called for.

Trad singers somewhere in the middle of the ol' Bell Curve.