I just assumed it was a sort of cigar-box fiddle, but with only two strings. Plaintive anyway. (Here is a picture of a cigar-box fiddle. It comes from what looks like a brilliant website I just found, when I put "cigar-box fiddle in my Webferret search engine.
That makes three songs mentioning "Nearer my God" - Titanic, Engine 143, and this. (The lady who wrote the words, Sarah Flower Adams, is buried in Harlow where she was born and lived, and there's a blue plaque on her house in the Old Town, so I feel a sort of local patriotic interest.)