How do bagpipes use drones in European folk music?

In European folk music, bagpipes utilize drones—pipes that sound a sustained, continuous note—to provide a sonorous foundation for the melody played on the chanter. These drones are typically tuned against the chanter using extendable joints, often sounding a bass note two octaves below the chanter's keynote or an octave apart in the case of multiple drones.1

The configuration of these pipes varies significantly across regional traditions:

• Scottish Highland bagpipe: Features two tenor drones and one bass drone, tuned an octave apart.1
• Central French cornemuse: Often uses a tenor drone held in the same stock as the chanter.1
• Irish union pipe: Employs three drones held in a single stock alongside "regulators," which are pipes that can be keyed to sound simple chords.1
• Northumbrian small pipes: Features four single-reed drones, of which three are typically used at a time.1

By maintaining a constant pitch while the chanter articulates the melody, drones create the characteristic, rich texture associated with bagpipe music.12