Halldorophones are purpose built electro acoustic string instrument, based on the premise of using electronically induced feedback in a coupled system of strings allowing for the creation of somewhat controlled, timbrally rich drones. In the halldorophone a positive feedback loop is induced in a coupled system of eight strings via electromagnetic pickups and a speaker cone in the soundbox of the instrument, more specifically the vibration of each string is individually detected with a dedicated single coil pickup the levels of which can be trimmed before being amplified and sent to the speaker which vibrates the whole system inducing feedback. Mimicking the major characteristics of a cello (upright, four string, fretless fingerboard, bowable string configuration) it also has four sympathetic strings running below the fingerboard (much like a viola d’amore or a barytone) which are not directly accessible for bowing or plucking but are rather electronically manipulated. All strings have the potential to be (electronically) included in or excluded from the feedback loop.
Feedbacking string instruments is a well known method of coloring and generating sound, as such the halldorophone introduces nothing fundamentally new but rather attempts to identify what is particular to this method of string excitation in comparison to other string instrument configurations and consequently what ergonomics and control-features are appropriate for such an instrument. The instrument has been developed through a few successive user centred design iterations (since around 2005) to include the features comprising the third iteration of the instrument existing today.
A paper describing the halldorophone was accepted at the NIME conference (New Interfaces for Musical Expression) in 2018, describing it in more detail. Downloadable here:
This website is an archive of projects involving halldorophones by year (corrections welcomed if you come across any inaccuracies). The instrument is a project of Halldór Úlfarsson, look down and to the left for his personal website.