The music is not coming from a speaker. The lightning is the speaker. A Tesla coil is not a transformer in the usual sense. It is a pair of tuned resonant circuits coupled loosely through air instead of iron, and the voltage gain comes from resonance rather than turns ratio. - Primary: a few turns of heavy copper tube in series with a capacitor bank, low inductance, huge peak current - Secondary: thousands of turns of fine enamelled wire, resonating against its own distributed capacitance plus a toroidal topload - Both tuned to the same frequency, 50 to 500 kilohertz Energy transfers between the two tanks each ring cycle. Terminal voltage climbs until the air can no longer hold it off, roughly 3 megavolts per metre, and a streamer punches into the room. The musical part is a modulation trick. A dual resonant solid state coil drives the primary with an IGBT bridge, locked to the ringing frequency by current feedback. That carrier sits far above hearing. Sound comes from an interrupt...