Although I'm not a fan of rap music, I have been impressed on those occasions when I've seen a "freestyle" rap performed. This involves the rapper improvising the rhymes as s/he goes along, to a solid beat.

Freestyling, to me, is the modern equivalent of the improvising that I've read was done by chanteymen. There were standard verses, of course, but the exigencies of the job at hand often required the chanteyman to "piece out" the song beyond the standard lyrics, based on the sources I've consulted. Some chanteys, apparently, were mostly improvised, and the version collected was what the singer happened to remember that day.

As to "Final Trawl" being useful as a halyard chantey, I haven't heard Fisher sing it, but I imagine it would need to be slowed down a bit. But you can get two good pulls on the two chorus lines in each verse -- "Sing *haul* away, ma *lad*die-O" -- which should work in getting a topsail hoisted, for example.

Jerry