This would be a good topic to ask the harp mailing list.
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The breastbone could be the neck, the pillar or the top of the harp. It wouldn't take any weight in real life so the harp would probably be plunky like a ukelele because you couldn't tune the strings up. The finger bones could be the tuning pegs and I like the idea of hair being used for strings. The hair could be wound around gut strings i.e. these strings have a core string, and are tightly wound with a finer string like wound steel strings on a guitar.