Nikola Tesla is best known for his revolutionary work in the field of electromagnetism in the late 19th and early 20th century. He is also one of the most important contributors to the birth of commercial electricity. The Tesla Coil is one of his most famous inventions.
Nikola Tesla (1856-1943) and one of his coils, c. 1899
The Tesla Coil is basically a high-frequency air-core transformer. It takes the output from a 120vAC to several kilovolt transformer & driver circuit and steps it up to an extremely high voltage. Voltages can get to be well above 1,000,000 volts and emit in the form of electrical arcs. Tesla coils are unique in the fact that they create extremely powerful electrical fields. Large coils have been known to wirelessly light up florescent lights up to 50 feet away, and because of the fact that it is an electric field that goes directly into the light and doesn't use the electrodes, even burned-out florescent lights will glow.
Tesla coils built by Syd Klinge for Coachella 2006
In 2007, Tesla enthusiasts Steve Ward and Jeff Larson constructed two musical Tesla Coils for the "Lightening on the Lawn Teslathon" in Wisonson. The music that you hear is coming from the sparks that these two identical high power solid state Tesla coils are generating. There are no speakers involved. The Tesla coils stand 7 feet tall, are spaced about 18 feet apart and are each capable of putting out over 12 foot of spark. The coils are controlled over a fiber optic link by a single laptop computer. Each coil is assigned to a midi channel which it responds to by playing notes that are programed into the computer software.
A longer clip of the concert (just under 10 minutes long) and can be seen here.