I think the saddest songs for me have to be those about the war. I studied WWI in some detail, particularly the Ypres Salient and have spent many hours in Flanders. I tried to go through No Mans Land in my mind whilst stood in Tyne Cot Cementry and couldn't get through it. I defy anyone to stand in a Flanders trench and try to get through Christmas in the Trenches or similar.
Bob Hambilton's song "Don't Let the Music Die"; Les Sullivan's "Roses of No Man's Land" all rank as WWI tear jerkers.
Happiest? LOADS. Up there amongst the top must rank the good lung-bursting songs such as Old Dun Cow.
Rhiannon