The difference, to my ears, between cajun and French and French-canadian, is that in Louisiana the French music came up against black music.Both the fiddle and accordion style are radically different from anything that developed in Canada, and the the presence of black music is the obvious extra ingredient. And the black and white musicians regularly played together in Louisiana in the period when the music was being created, much more so than in the English-speaking parts of southern USA. The fiddle style is extremely distinctive, as is the accordion stuff, developed largely by playing the accordion "backwards"(in G on a C box) which is exactly how the blues harmonica style developed: by playing in the suck key instead of the blow.