Double D is good for lots of stuff besides "Celtic" chunes. For example, I used to show people how I could play the banjo on my guitar in it. But that was before I grew up.

You can also use it to imitate the Beatles imitating Ravi Shankar imitating traditional cittarh music. I spelled that after "catarrh" because I do not remember at the moment how it should be spelt. And its good for certain kinds of artsy fartsy stuff. Besides it gives you two instruments for the price of one.