And I have to agree that rap might not be considered music given the fact that it lacks the element of melody.
okay, so I guess you need the definition of melody, too:
//a sequence of single notes that is musically satisfying//
even though it's spoken~sung word, each word and syllable is a note. Maybe a G, then a G# or A even! The voice is an instrument, and everything coming out of it is melodious. Just say the word 'melodious' and you'll understand! haha