The scripture said, "...Is any merry? let him sing psalms." (James 5:13, KJV). Besides, Ephesians 5:19 says, "Speaking to yourselves in psalms and hymns and spiritual songs, singing and making melody in your heart to the Lord" (cf. Colossians 3:16, KJV).
In view of the foregoing scriptures, the so-called "rap genre of music" is alien and foreign to the teaching of the scriptures in respect to the kind of songs that true believer in Christ should be involved.