@ Gordon Jackson: have you ever seen Fisherman's Friends on stage? They DON'T sing all of their songs a cappella; guitars and orher instruments very much in evidence, I too would prefer the unaccompanied versions of shanties.

Hi Tatie, no I've never seen them on stage, but that wasn't my point. My point was that in the film they are shown singing unaccompanied, and yet guitars et al are clearly heard. There is no sign of a PA that could have provided backing tracks. Perhaps some might consider it a bit anorakish, but were I standing in the harbour listening to unaccompanied singing, I'd have been looking around for the guitarist!