hi recently I build the high voltage spark using ignition coil
here is the thread for that
now I want to use that arc to create music
i tried connecting amplified music to the input of mosfet but that does not seems to work.
after bit of search i found out that i need something like modulated pwm but couldn't find any information on how to create it
so does any one know how can i create modulated pwm

 

In your thread about the high voltage generator I said how the 555 can be damaged if the pot is turned too low, that the frequency of the 555 is probably to low to PWM it to make music and and how to make PWM:

"The old datasheet for a 555 showed how to PWM it but the new datasheet does not. Google has many articles about it but many of them Do Not Work!
To make PWM, remove the 10nF capacitor C2 at the pin 5 of the 555 then capacitor-couple the audio signal to it."

 

I agree with Audioguru again in that the Internet has thousands of circuits which don't work. You may want to give this a read and note how the audio input is applied to the 555. I have no idea if this circuit will or will not work as I never tried it. You seem to want to create a High Voltage Plasma Arc Speaker. Something I am unsure of is how the audio signal going negative is handled by the 555 pin 5 control. It looks like the circuit in the link applies a positive bias at a glance. A simple Google of "High Voltage Plasma Arc Speaker" should get you plenty of circuits to try and apply to what you have.

Ron

 

Here is what a datasheet shows about making PWM on a 555 oscillator: