Regulator
semidrone, retunable during playing
Each of the stopped semidrones; They stay mute until one of their closed keys is activated; Introduced 2nd half 18th century, presumably by John Egan, a bagpipe maker in Dublin; Nowadays a set of 3 regulators is common.
Striking the keys in juxtaposition on 3 regulators simultaneously gives: f♯¹ (tenor only), and 4 chords: g-d¹-g¹, a-f♯¹-a¹, b-g¹-b¹, c¹-a¹-c².
NB: Example(s) to be replaced with staff-notation.
Leydi, Roberto: La zampogna in Europa. Como, 1979, p.83-85, 88.
Breathnach, Breandán: The Irish pipes. In: The bagpipes in Europe, 1 (1976), ➺ p.6.
Garvin, Wilbert: The Irish bagpipes: their construction and maintenance [Belfast 1978, Blackstaff Press]. Foreword by Breandán Breathnach. Kells, 1988 (2), p.35.