The thing with intellectual rights is it is all about the lyrics and/or melody. Chord progressions are not subject to copyright. So MK writes the song, comes up with melody and whatever anyone contributes after that - unless they change the lyrics or melody the song is still 100% MKs. That is how the music industry works.
Well, thats in legal terms.
In moral terms, if you create and added something, you and everybody involved knows that you added a part that comes from you. The fact that there is not any law that protect you, doesnt means its not true.
At least, thats my point of view. When you create culture (and music is culture, although its taxed differently to the books) its not the same that when you built a house or a table...