The D pipes are most often Employed in ensembles, when the flat-pitched pipes are more often utilized for solo playing – frequently fiddlers will tune down their instrument to play having a piper's flat set, but the inflexibility of other devices used in Irish music (accordions, flutes, and many others.) https://vocal.media/art/elevating-craftsmanship-the-charm-of-ceramic-pipes-by-cosmos-art-ceramics