re: Bands whose sound changed dramatically: cite evidence

Random one that popped in my head is Styx. Kind of a band you can make fun of, but then they do have some really decent songs (Renegade, Too Much Time On My Hands, etc). Then they have the other hits that they are known for that just sound way different (Sail Away, Lady, Mr. Roboto, etc.). It's not necessarily a distinct timeline change. They just put out very different songs over time.