The Halldorophone in the Joker and Chernobyl Soundtracks
Icelandic composer and cellist Hildur Guðnadóttir used the halldorophone as the central instrument in two of the most acclaimed film and television scores of 2019: the HBO miniseries Chernobyl and Todd Phillips' psychological thriller Joker, starring Joaquin Phoenix.
The Joker score won Guðnadóttir the Academy Award for Best Original Score, the BAFTA Award for Best Original Music, and the Golden Globe Award for Best Original Score — making her the first solo female composer to win all three for the same work. The Chernobyl score won the Primetime Emmy Award for Outstanding Music Composition, a BAFTA TV Award, and the Grammy Award for Best Score Soundtrack for Visual Media.
The Instrument
The halldorophone is an electroacoustic string instrument built around the deliberate use of audio feedback. It was designed and built by Halldór Úlfarsson, who first developed it as his MFA graduation piece at what is now Aalto University in Helsinki in 2008.
The instrument has eight strings: four main strings played with a bow, and four sympathetic strings that resonate through the feedback system. Each string has a dedicated pickup. The signals from these pickups are mixed and fed back through a speaker mounted inside the instrument body, creating a closed loop of mechanical vibration. The player controls the instrument by adjusting gain levels and bowing technique, guiding the flow of self-sustaining resonance.
Hildur Guðnadóttir has owned and played halldorophones since 2012, when Úlfarsson built her the first instrument incorporating sympathetic strings. She has referred to the halldorophone as her primary instrument.
Joker (2019)
All the principal themes in the Joker score were composed and performed on the halldorophone before the film went into production. Director Todd Phillips played Guðnadóttir's recordings on set during filming, allowing the music to directly shape the performances of the cast.
The halldorophone is the instrument heard in the bathroom dance sequence — one of the most discussed scenes in the film. The music for that scene was written in advance; Phoenix improvised the choreography to Guðnadóttir's recording on the day of filming.
The full score was ultimately recorded with a large orchestra, but the halldorophone themes underpin the entire work. As Guðnadóttir has described, all the strange sounds in the score — including the sounds associated with Arthur going into the fridge — were played live on the halldorophone, run through a four-stack of amplifiers, with no computer processing.
Chernobyl (2019)
The Chernobyl score was composed concurrently with Joker. Guðnadóttir traveled to the decommissioned Ignalina Nuclear Power Plant in Lithuania — the location used for filming — before production began, recording the ambient sounds of the facility. The score is built almost entirely from those field recordings, with Guðnadóttir's voice as the only additional human element.
The halldorophone does not appear prominently in the Chernobyl score in the same way as in Joker; the two works represent very different sound worlds, composed simultaneously.
The Instruments
Halldór Úlfarsson has built three halldorophones for Hildur Guðnadóttir over the course of their collaboration:
- 2012 — Prototype exploring the inclusion of sympathetic strings
- 2014 — Refined sympathetic-strings version, soundbox by Jóhann Gunnarsson, electronics by Úlfarsson and Christian Zollner
- 2023 — Double speaker instrument
Further Reading
- Halldorophone — Wikipedia
- Hildur Guðnadóttir — Wikipedia
- Bela Blog Interview with Halldór Úlfarsson (2025)
- Designboom feature (2024)