Music is a very strong tool used to pass messages intentionally, which can either be destructive or non-destructive. One can use music to communicate an idea, thoughts and perception about anything.
For this cause, He communicates his sunesis and cogitations about God to the world through songs. After his contemplation through the Scriptures, and the messages of his Man of God, he could not stay silence.
He may not have the chance to stand on the pulpit to preach to the whole world but he puts it in words and add nice sounds to it for the whole world to hear. These songs are new testament songs. Spirit filled songs. They edify, bring hope and faith to the hearers.