Why Does That Music Have a Note That Never Stops? Something Fixed to Hear Against

A sustained note held throughout a piece supplies a fixed reference against which everything else is heard. Each note of the melody forms an interval with it, and because the reference does not move, the listener perceives those intervals directly rather than inferring a harmony from a sequence of chords, which is a different way of organising music from the one Western harmony uses. It also establishes the tonic unambiguously, so the music cannot wander away from its home note without that being audible immediately. And it supplies a continuous sound that fills the gaps between melodic phrases, which matters for solo performance and for instruments that cannot sustain.

Many traditions developed instruments producing a drone alongside a melody:

• •Bagpipes across Europe, north Africa and western Asia, with separate pipes sounding fixed notes
• •The hurdy-gurdy, where a wheel bows melody and drone strings together
• •The Indian tanpura, whose only function is producing a drone
• •Sitars and comparable instruments with sympathetic strings that resonate continuously
• •Fiddles in several traditions played with a bow touching two strings at once
• •Organs with a pedal note held beneath moving parts

A fixed reference works well with musical systems that are modal rather than harmonic, and the relationship is not accidental. Where music stays within a single mode with a fixed tonic, a drone on that tonic is consonant throughout and reinforces the mode. Where music changes key, a fixed note becomes dissonant as soon as the key moves, which is why Western art music abandoned the drone as harmonic movement became central and why its reappearance in the twentieth century accompanied a deliberate turn away from that movement. The drone also makes fine tuning audible, since a note slightly out of tune against a sustained reference beats audibly, which is why traditions using drones develop precise tuning and why singers in those traditions are trained against one.

Instruments producing a continuous note face a tuning problem that intermittent instruments do not. Anything held for minutes must not drift, which rules out materials and mechanisms that change with warmth and humidity, and bagpipe players spend a substantial part of any performance adjusting their drones for exactly that reason, with the instrument warming as it is played. Reeds must be stable and are selected and adjusted for it. Strings stretch and must be retuned constantly, which is why a tanpura player retunes between pieces and sometimes during them. Electronic drone boxes removed the problem entirely and are now standard in Indian classical performance, which purists objected to and which is nearly universal, since the alternative is a musician occupied full-time with a single note.

The device is far from historical. Indian classical performance begins with a drone established before anything else and maintained throughout, now frequently by an electronic box rather than a player. Minimalist composers from the 1960s built extended works on sustained tones, explicitly drawing on non-Western practice. Film scoring uses sustained low notes to establish atmosphere and to avoid committing to a harmony. Several electronic and rock traditions use them heavily. And the practice of tuning to a drone is standard in teaching intonation, since it gives a student an unambiguous reference that a piano cannot supply, the piano being tuned in a compromise that is slightly wrong everywhere.

A sustained note supplies a fixed reference, so each melodic note forms an audible interval with it and the tonic is never in doubt. Bagpipes, the hurdy-gurdy and the tanpura are built around producing one. It suits modal music with a fixed tonic and becomes dissonant as soon as the key changes, which is why Western harmony abandoned it.