These are two gigantic solid state musical Tesla Coils. A Tesla Coil is a special type of transformer invented by Nikola Tesla that is able to generating extremely large voltages using a phenomenon known as electrical resonance. Each coil in this video is capable of generating a 13 foot spark. This equates to about 500,000 volts of electricity.
The primary drive system for the coils consists of high power semiconductors arranged into an H-Bridge switching configuration. During a spark event, the coil is pulsed on for a few hundred millionths of a second. During this short time, thousands of amps circulate within the primary tank circuit and the energy is coupled into the secondary resonator through magnetism.
So what appears to be a continuous burst of sparks is actually a specific number of sparks generated per second. By modulating the number of sparks that emit from the coil each second, different tones can be produced by the coils.
These coils were constructed by Eric Goodchild and Steven Caton.
Eric Goodchild is currently an EE student at ASU Polytechnic.
His personal website is: http://www.goodchildengineering.net/
Steven Caton is currently an EE student at UCLA
His personal website is: http://stevencaton.com/