If you have doubts about the beauty of all the different ethnic and cultural nooks and crannies in America, this act may well erase them. Sweet Crude is straight out of Louisiana and they proudly sing out in French and in English. As a matter of fact, one of their desires is to preserve the relevancy of their beautiful French language in the arts. Fun, energetic, bayou-y, and just plain talented, Sweet Crude is at the Iron Horse tonight. It’s so trite, but I can’t resist: Laissez les bontemps rouler!!! 7 p.m. Iron Horse Music Hall, 20 Center St., Northampton.