The haunting song, played on Irish Uillean bagpipes, is “Caoineadh Cu Chulainn (Lament)” by Davey Spillane.
Uillean pipes are the national bagpipe of Ireland. In Irish, píoba uilleann mean literally “pipes of the elbow” because of the method of inflation. The bag of the uilleann pipes is inflated by means of a small set of bellows strapped around the waist and the right arm.
The uilleann pipes are distinguished from many other forms of bagpipes by their tone and wide range of notes. They have a different harmonic structure, sounding sweeter and quieter than many other bagpipes, such as the Great Irish Warpipes, Great Highland (or Scottish) Bagpipes or the Italian Zampognas.
H/t FOTM’s Irish friend, LoneWolf!