I'm not sure what you mean by that. King of Hollywood is the only Eagles song where Don sings the lower part and Glenn sings the higher part in conjunction with him. It's a one-off. When they sang Good Day In Hell Glenn was more prominent but Don sang with him throughout. On their other duets they have each sung separate verses or sections (Doolin-Dalton, Ol'55, What Do I Do With My Heart, How Long).