I have absolute pitch; I can tell the pitch of any musical note I hear without any reference at all. I can also produce any pitch within my vocal or whistling range without a reference. This all comes completely naturally to me, and I don't have to think about it. Listening to this rap song, I noticed something strange.
The article talks about the melody of the song, but the rapper isn't singing. Of course, his rapping voice still has a pitch but it's actually not obvious to me what note he's "singing". If I listen very hard, I can still pick out the pitches of his notes (like how he centers on D). However, it is much much harder for me to tell the pitch of a speaking voice (or rapping voice) than a singing voice. This leads me to believe that there is a separate, functionally discrete part of my brain dedicated to processing music.
It also perhaps explains why I don't like rap music that much; it feels like my brain processes it as though it is spoken word rather than music, creating a somewhat strange and unmusical experience.