Where do you find the singing sword in fable?

Dude, i don't actually know where to find it, but it has got to have links with a hidden demon door as it also has a miniature demon door badge on the sword itself, from previous images that I've seen.

!!Update!!

I got it from the box in your treasury room after climbing the gold to get the key and loosing all the gold to get to the box. I think it randomly gives you a legendary item when you open it. Hopefully you get it.