Bagpipes are a type of musical instrument from Earth that use a series of reeds fed from a constant reservoir of air in the form of a bag. They are most often associated with Scotland, and the type of bagpipe from that region is known as a Great Highland Bagpipe.
Montgomery Scott learned to play the bagpipes from his grandfather. (TOS novel: Dreadnought!) He owned a set of bagpipes that he kept in his quarters on board the USS Enterprise. (TOS episode: "By Any Other Name") After the battle with Khan Noonien Singh in which Captain Spock apparently gave his life to save the Enterprise, Scott played Amazing Grace on his bagpipes as Spock's torpedo tube was loaded into the launcher to be fired over the Genesis Planet. (TOS movie: Star Trek II: The Wrath of Khan) Scott later helped cure the humpback whales George and Gracie of a mysterious illness by playing his bagpipes for them, relieving their loneliness and encouraging them to sing. (TOS - Strange New Worlds IV short story: "Scotty's Song")