My coil is actually a $300 kit from Eastern Voltage Research. It is a very powerful Dual Resonant coil capable of 20-30" sparks, which is unheard of for such a small design. The secondary is only 11" tall!!!
It's driver is simple is some regards and complex in others.
It is self tuning, the driver circuitry applies a step response and measures the coils resonant frequency with a current sensor and turns around and drives it at it's natural resonance no matter what it is.
The actual power circuit is a simple DC voltage doubler from the 120V AC mains to create 340V DC. Then two IGBTs turn the DC back into AC to drive the primary. It's scary, system is pumping 340V DC @ 350 Amps (!!!!) into the primary coil. But only for 100 uS at a frequency of 60 - 100 Hz.
Downside is it doesn't have a great frequency range without risking burnout and it's only monophonic. You need a much bigger non-DR coil to do polyphonic.
This is my only experience with these new fancy digital coils. Not like the old analog beer bottle coils I built in high school.