We got the plans and some of the parts from Eastern Voltage Research.
A brief explanation of how tesla coils work:
The Tesla Coil generates up to ~50,000 volts at the top "toroid", which causes the air around the coil to ionize and conduct electricity. The electricity "leaks" into the air to create the arcs. With a MIDI (musical instrument digital interface) connection, the arcs can be tuned to resonate at different frequencies and play music. Air ionizes when about 1,000 volts per inch of air gap is applied, so we can generate arcs up to about 4 feet. The Tesla coil works by generating low-ish voltage (~300V) and high current in the primary coil and then transferring that energy into the secondary coil tower to create a very high voltage / low current discharge that generates the arcs.
It was a good project for our team to do because it gave us a broader view of the basic behaviors of electricity and the different kinds of electronics beyond the FRC control system. A year later, we built a second tesla coil so we could have a higher range of notes and so they could play in a 'duet' together. We also created an accompanying synced laser light show. The tesla coils make regular appearances at our team events and parties, both outdoors and in!