This article is from the Bagpipe FAQ, by Denise McNickle firstname.lastname@example.org with numerous contributions by others.
The Uilleann pipe (UP) is a type of bagpipe native to Ireland. The UP is
mechanically somewhat complex, and is normally meant to be played while
seated. It has a range of up to 2 octaves, and is usually pitched in the key
of D. The piper inflates the bag by operating a bellows with one arm, and
maintains pressure on the bag with the other arm. Main UP components include a
bag, a bellows, a double-reed chanter, zero or more drones (usually three),
and zero or more stopped pipes called regulators (usually three).