Military ships did not use chanties as a rule nor would the fiddler have plyed while the crew worked. The "literature" you referenced was half right about the fiddler entertaining the crew. In the rare off hours they would have provided their own entertainment on board the ships. This would have been in the form of music played or sung unaccompanied, and story telling. The music would have been what they knew so the fiddler would have played Irish fiddle tunes of the time. the songs would have also been from the sailors' backgrounds and MAY have included popular Civil War songs at the time.

Roll, Alabama, Roll was a chanty used on merchant ships after the Alabama was sunk.