Be careful what is termed as 'authentic' as well. I once heard the comment that an 'authentic' shanty should be sung in complete unison with no harmonies. The reason given was that the sailors at the time would be working hard and have no time harmony singing! Well, sorry, but until someone proves otherwise to me I doubt very much singing a natural harmony, as people do all the time, is any more difficult or takes any longer than singing in unison. I accept that most people will sing unison when faced with a song or chorus but in any group you will find a percentage who automaticaly sing above and below the line. Often both and often with no idea they are doing it!

Cheers

Dave