I want my solid state Tesla coil to play music. I built it to only accept square wave input. Does anyone know howI take a normal melody (no voice,) only keep the main soundtrack (no bass or anything else) and convert it into pure and simple square wave?
The task you are after is easier to approach from the other end:
Get some sheet music. What you need is a single voice melody. An example. 1.1 A MIDI file of the song, if available, may save you a lot of manual work.
Convert pitches into frequencies. C (the note starting the example song) is 261 Hz, any half tone up is up by 12-th root of 2
Generate the square waves for each note by whatever means available (e.g. Arduino) and feed it into your Tesla coil setup. Take care to deal with different note durations. You may want to create 5% or 10% silence at the end of each note in order to distinguish the beat when some note repeat.
p.s. Also take care not to burn anything, yourself included.
p.s.2 You can get a lot of inspiration from what 1980s computers and game consoles did (see Retrocomputing.SE, a lot of 1980s hardware had only square waves available).
This is the same approach in modern hardware made for completely different purpose.