~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. 3.5 Simulation 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. 5. CONCLUSIONS 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. 6. REFERENCES [1] N. Tesla, "System of Electric Lighting," Patent US 454 622, June 23, 1891. [Online]. Available: http: //www.google.com/patents/US454622 [2] R. Uth, "Inside the Lab - The Tesla Coil," http://www. pbs.org/tesla/ins/lab_tescoil.html, accessed January 29th 2015. [3] P. Belohlavek and J. Wagner, Innovation: The Lessons of Nikola Tesla. Blue Eagle Group, 2008. [4] S. Connor, Private Communication, 2015. [5] J. DiPrima, Private Communication, 2015. [6] A. Parekh, "Tesla Coil Music," http://hackedgadgets.com/2006/06/30/tesla-coil-music/, accessed January 31st 2015. [7] T. Mrosko, "An Electrifying Performance," Case Alumnus, vol. 22, no. 3, p. 7, 2010. [8] 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 -
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