The bands that play in the lobby, casino and most venues should fit the bill. I forget their name, but on our cruise on the Dream the band that played evenings in Ocean Plaza played mostly country and oldies.
A Bad Day At Sea [with power] Always Beats A Good Day At Work
Carnival: Glory 2004, Destiny 2008, Splendor 2009, Freedom 2011, Valor 2012, Dream 2013
Celebrity: Summit 2011
Princess: Ruby 2010, 2014, Caribbean 2013, Coral 2014