Apologies for thread drift in the above post.

I like most of the suggestions already offered and am also a firm believer in the value of making people feel comfortable so that performance is possible. But I also believe in the value of background preparation for the novice singer (e.g. the exercises suggested) and in the reality of baby steps.
I've had occasion to support some people who lacked confidence in their singing ability and found that one thing that often worked was to present them with something that they didn't think of as a 'song' ( a playground skipping song, a totally silly comic song like My Grandfather's Socks etc.) where they could hide behind a persona and not be under pressure to produce lovely sounds.

If a novice wanted to sing Gordeanna McCulloch's version of The Cruel Mother, I think I might start with the kids' version from The Dubliners before perhaps moving to Lorna Campbell's version (tune on the melodically restricted side) and -- via (Burns' collected version) Fine Flowers in the Valley -- eventually to Gordeanna's demanding tune. My hope would be that the repetition of narrative would provide insight into the emotional depths and assist in the story-telling aspect of ballad-singing.
BUT, in the work-up to this outcome, I would be offering the distraction of rhythmic chorus songs such as shanties; little, sweet chorus songs like Matt McGinn's Coorie Doon; and comic songs such as some of the Scottish CND output from the Ding Dong Dollar booklets.