Haven't found the reference (yet) but I did find this:Andrew wrote:They're all items that are mentioned as being found in Smaug's horde in The Hobbit; but not necessarily as belonging to those Dwarves.
“Fili and Kili were almost in merry mood, and finding still hanging there many golden harps strung with silver they took them and struck them; and being magical (and also untouched by the dragon, who had small interest in music) they were still in tune.”
I like it.