An anecdote to illustrate how much you can trust mentions of musical instruments in songs. I met someone who'd been playing their hurdy-gurdy at an event in France when an elderly British gent came up to ask what the heck it was it was, as he'd never seen one before.

The old guy asking was Donovan, something like 30 years after writing this:

http://en.wikipedia.org/wiki/Hurdy_Gurdy_Man

And I could never imagine the Minstrel Boy going off to war with his wild harp slung behind him getting very far or being very militarily effective, however wild his harp might have been.