About the attire - all other employees/entertainment wear specific clothing to add to the atmosphere that is part of WDW. The video clip I watched was disappointing because the musicians wore casual street clothing. I expect more from an act at WDW.
And yes, I do like Celtic music. Husband and I are going out in a few minutes to the Pickled Onion, where friends of ours will be playing some guitar, penny whistle, and fiddle music.