Mark Barton did the Tesla effects. Pictured above are three Tesla coils that I have built over the years. It operates at 430 KHz. In the middle is a traditional spark-gap coil design. On the right is a plasma lamp sculpture powered by a solid-state Tesla coil utilizing a flyback transformer.
Tesla coils are relatively simple, and resonably easy to construct.
Despite the fact that they were invented over 100 years ago, they are still popular and fascinating devices. The problem is the lack of good, solid information. As mentioned, Tesla coils are resonant transformers. This implies that there is a specific frequency at which they operate - the resonant frequency . What determines this resonant frequency is the secondary coil - a complex LCR network.