Feadain (singular or plural?)
plural: = singular?; (with) definite article: ?term used for an instrument as a whole (e.g. a very good set / an old set / a rare set)
According to Ledwich (if interpreted correctly), this term was used to denominate either a "set of pipes", or all the [sound] pipes.
Ledwich, Edward: The antiquities of Ireland [1790]. Dublin, 1804 (2), p.250.