The Uilleann pipes are distinguished from many other forms of bagpipes by their sweet tone and wide range of notes – the chanter has a range of two full octaves, including sharps and flats – together with the unique blend of chanter, drones, and regulators. The regulators are equipped with keys enabling the piper to play simple chords, giving a rhythmic and harmonic accompaniment as needed. The Uilleann pipes have a unique harmonic structure, sounding sweeter and quieter than many other bagpipes, such as the Great Irish Warpipes or Great Highland Bagpipes. The Uilleann pipes are usually played indoors, and almost always played sitting down.