Yes, you can add a melody but you will have to play it on a midi instrument if you expect the melody to be that of the old gospel song. In other words, a live human has to be behind the playing of the melody in some shape or form.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.