Use the adjective unitary to describe something that has or desires unity, or oneness.
Just as the United States are joined together as one, words such as united and unity have to do with oneness or coming together into a single entity. The same is true of unitary. A unitary concert brings different kinds of music together. Unitary philosophy deals with how everything is part of a whole. There are many technical uses of this word, but they all have to do with uniting something.