Neill's instrument is actually the mutantrumpet, designed with help from Robert Moog, which consists extra bells and valves, and electrical modifications that allow him to control computer variables with the valves. The first mutantrumpet had three bells, six valves, a trombone slide and an analog processing system. At the Steim Studios in Amsterdam he then developed a MIDI-capable mutantrumpet, which contained more switches, knobs, and pressure-sensitive pads so as to allow greater control over the sound and visuals of his sound installations.