Shanties were work songs - the shantymen were aiming to get the work done, not make 'pretty' sounds.
When McColl, Lloyd et al introduced the shanties in the early days they attempted to strike a balance between the function of the songs and the aesthetics - personally I thought they did a good job of it - it's stayed with me for forty years.
For me, the best of the shanty singers don't let you forget what they are about. Lloyd once remarked about a group who were notorious for producing pretty and complex harmonies on shanties "They sound very nice but they wouldn't get a rowing boat across a park lake".
As far as authenticity, the recordings made in the 50s of A H Rasmussen stand out a mile. The BBC mucked up some great shanty singing from a shantyman named Stanley Slade by adding a BBC chorus, complete, I believe, with dinner suits and bow ties. Stan Hugill had a reputation as a good shantyman but I have never made up my mind about his singing.
The Library of Congress released 2 albums entitled 'American Sea Songs and Shanties' from recordings made in the 30s and 40s.
The most enjoyable set of shanties on record by revival singers are, IMO those on the two Argo albums by the Critics Group released in the late 6os.
A Dub friend once told me that the nearest he'd ever heard to genuine shanty singing was from a gang of men on a Dublin street pulling a large electrical cable through an underground pipe, with the ganger singing out the instructions and the labourers grunting the response in time to the work.
Jim Carroll