The Nu, or Chromatic Didgeridoo, was invented by Erik Nugent 1). Only one known instrument exists.
The Keyed Didgeridoo (also called the Orchestral Didgeridoo) was built some time around 1990 by Graham Wiggins. Only one known instrument exists.
Boudophone, also called the Korn Bass was invented by David Defois. This instrument uses a slide much like a trombone but the slide is in three telescoping section that are geared together so that the action of sliding the instrument is smooth and consistent. This system also gives the instrument a range of just shy of 2 octaves from G0 – F#2.
Didjeribone invented by Charlie McMahon 2) uses a simple slide mechanism of a well fitted telescoping tube.
Slide Didge, Timber Slide Didge, and Triple Slide Didge are made by Scott Dunbar. 3) The Slide Didge resembles the simple mechanism of the Didjeribone and works the same for the most part, with the Timbre Slide Didge being made from wood and requiring a wider bore and aperture change with the thicker material of wood. The Triple Slide Didge uses Three sections of telescoping tubing to extend allowing for a wider range one the instrument.
Erik Nugent also invented the Nu mouthpiece, which is a mouthpiece that has an orifice shaped like that of a didgeridoo and can be used as a replacement mouthpiece for various wind and brass instruments. The mouthpiece works as a replacement for the mouthpiece of a baritone saxophone, trombone, euphonium, tuba and potentially bass clarinet.
William Thoren Developed a wider oval shaped mouthpiece that allows for very low notes to be played using various lip techniques. One such technique involves playing part of the undertone series.
David Defois website- 4)
William Thoren demonstrating the technique he calls Multi Drone, an undertone series can clearly be heard early in the video- 5)
The Nu instrument and Nu Mouthpieces are no longer being manufactured, and Erik Nugent is instead focusing on developing and building concert flutes.
KORN BASS INTERVIEW 6)
NU INFORMATION 7)