Northumbrian smallpipes (plurale tantum)
Bagpipe, bellows-blown: 2 stocks (a: single chanter / b: 4 drones in 1 stock)
Instruments with 4 drones seem to be more "modern" than the ones with 3 drones; NB¹ (plurale tantum): The term is also used when referring to 1 instrument only;
NB²: ➺ Northumbrian pipes; NB³: ➺ Parlour pipe, Shuttle pipe.
Bibby-Wilson, Kim & Moore, Anne (eds.): Morpeth Chantry Bagpipe Museum: souvenir guide. Newcastle upon Tyne, 2003, p.9 (Northumbrian small pipes).