The halldorophone is a cello-like, feedback instrument, developed over the past decade by Halldór Úlfarsson. The instrument is well-established in experimental music circles and gaining wider recognition thanks to it’s use by composer and cellist Hildur Guðnadóttir in film scores, including her Oscar nominated music for Joker (2019). The halldorophone utilises a simple system, whereby the vibration of each string is detected by a pickup, amplified and routed to a speaker embedded in the back of the instrument. By adding gain to individual strings in the feedback loop, the instrument’s response can become rapidly complex, potentially spinning out of control. While every musical performance of a piece is unique in some way and contingent on its particular moment and situation in time, the unstable nature of the halldorophone exacerbates this condition. Players describe the halldorophone as ‘unpredictable’, ‘very much alive’ and as [having] ‘its own ideas’, even tiny changes to their body position in performance might produce unexpected effects [5]. In this NIME premiere for the instrument, cellist Nicole Robson will perform a piece for a new digitally endowed halldorophone, and the title of the piece – Dual/Duel/Duet – acknowledges the active role of the instrument in shaping the composition and performance.