The Halldorophone#5 was built, partly, under the tutelage of finnish, master guitar-maker Kari Nieminen at the University of Art and Design Helsinki. The Electronics and pickups are designed and built (for the most part) by audio engineer Jonte Knif.
More about Halldorophones here.
Noteable improvements from previous instruments are- individual volume controls for each string complete with aux channels for individual string signals (allowing for volume pedals and effects to be accurately applied). The timbre is eminently richer than in previous versions, the cello tuning is also very complementary to the feedback effect and because main characteristics are so close to a cello this instrument is quite accessible to classically trained cellists.
These instruments are in further development, as of 2010 three more are being built.
Halldorophone#5 is in good hands on fairly permanent loan to Hildur Guðnadóttir who is using it well.
Here´s some footage of Hildur the first time she tried the instrument.
And here´s some recent escapades of the Halldorophone#5-
Prominent in a Knife track, 2009, played by Hildur
In a composition by Sunn O)))’s Stephen O’malley, 2009, played by Hildur
Explained and played at Sommercamp Workstation by Labor for kunst und medien, 2009, Berlin
“Talent” show at DesignHuis, Dutch Design Week, Eindhoven, 2008, curated by Lee Edelkoort