reporter: that unforgettable moment when president obama chose to heal a nation after the charleston church shooting not with a speech but with a song. and that church organ somehow kicking in just at the right time. that saved a wretch like me reporter: we couldn t see charles miller, but we could hear him. i once my organ playing wasn t planned with the white house. it was impromptu. reporter: the 33-year-old musician invited to play at the funeral service of his friend, reverend clementa pinckney, says he didn t take his cue from the president, but from a higher power. i just kind of let the lord lead me at that time. reporter: in church lingo it s called backing the preacher up. so, miller took a bold step and decided to back the president up. he started singing amazing grace and i just came in right behind him.