Should Toby Keith Sue Sebastian Mikael?

Are four (4) prominent and clearly-heard notes in common between songs reason enough to instigate a copyright infringement lawsuit? One answer could be found in comparing this hypothetical (or not) Toby Keith v. Sebastian Mikael copyright infringement case to the actual Marvin Gaye v. Robin Thicke copyright infringement case in which NO notes were in common between the songs. If one can sue when the similarity is only STYLE and NOT melody, surely one can sue when the similarity is MELODY.