~ICMC 2015 - Sept. 25 - Oct. 1, 2015 - CEMI, University of North Texas
Figure 4. The virtual Chime Red software interface.
thesizer inside their digital workstations and design sounds
for their musical works using an interface that is familiar to
them. Standard MIDI controller hardware can be easily assigned to the knobs, sliders and buttons of the interface to
provide real-time sound manipulation capabilities with visual
feedback. Reaktor also provides preset creation and preset
morphing functionality which enables sound artists to build a
collection of sounds to be recalled during performances and
to merge previously created presets for sound designing purposes.
An audio engine is included within the virtual Chime Red
which simulates the sound of a Tesla coil. This helps composers write music for the coils when they are unable to access the Chime Red hardware or the coils themselves. The
synthesizer emulates the sound of Tesla coils using pulsewave oscillators, a digital noise source modulated by the oscillators and a single pole high pass filter. The width of the
pulse oscillator, the level of the noise source, the cutoff of the
filter and the level of the output are all adjustable via the software interface. This allows users to emulate the sound of the
specific Tesla coils for which they are composing.
Excluding the simulator timbre controls, all of the parameter
controls on the panel of the virtual module both output MIDI
control change messages to the hardware Chime Red unit and
control the parameters of the simulated software Tesla coil
sound. This delivers a seamless integration between the virtual composition environment and the hardware performance
environment. The Chime Red hardware is also equipped with
an on-board speaker that outputs the pulse data that is sent to
the coils in real time. This provides another opportunity to
review the output of the system before activating the coils.
4. FUTURE WORK
Despite all of the newly implemented musical parameters,
there remain limitations which will need to be overcome in
order to continue to bring new musical expressiveness to Tesla
coil performances. The most fundamental of these limitations
is that due to the binary nature of switching IGBTs, the oscillator wave-shapes are all based on full-scale pulses. As
alluded to by the planned PCM mode, future work will focus
on allowing the system to produce arbitrary shapes of waveforms and output PCM audio directly. The optical charge outputs of the unit have also been attached in anticipation of an
advanced Tesla coil power supply that is also under development. This power supply will allow offline Tesla coils to
make full use of this new control system.
This paper has presented a new system for musically controlling Tesla coils, bringing them a step closer to being fully realized as musical instruments in their own right. The system
provides composers with a sizable array of expressive parameters with which to craft new and interesting sounds and will
enable a new range of music to be produced by the coils. To
make the best use of this new functionality, a synthesizer-like
software interface was built which conforms to standard electronic music composition work-flows and provides a method
of organizing and manipulating sounds that have been designed. A synthesizer which emulates the sound of the instruments was also implemented as a part of the software interface to aid in offline composition for Tesla coils.
All of these elements combine to create a system that brings
intuitive sound design and advanced compositional possibilities to Tesla coils, and enables new, complex, highly polyphonic and expressive music to be created with them.
 N. Tesla, "System of Electric Lighting," Patent US
454 622, June 23, 1891. [Online]. Available: http:
 R. Uth, "Inside the Lab - The Tesla Coil," http://www.
pbs.org/tesla/ins/lab_tescoil.html, accessed January 29th
 P. Belohlavek and J. Wagner, Innovation: The Lessons of
Nikola Tesla. Blue Eagle Group, 2008.
 S. Connor, Private Communication, 2015.
 J. DiPrima, Private Communication, 2015.
 A. Parekh, "Tesla Coil Music,"
accessed January 31st 2015.
 T. Mrosko, "An Electrifying Performance," Case Alumnus, vol. 22, no. 3, p. 7, 2010.
 B. Johnston, J. Bailey, and D. McKinnon, "NICO: An
Open-Source Interface, Bridging the Gap Between Musician and Tesla Coil," in Proceedings of the 2014 International Computer Music Conference, Greece, 2014.
- 205 -