flame for plasma transducer

Sure, not a problem. You can run a flame (MAPP, Propane..etc) seed it with a salt, something like KCl (aq). Put a couple of electrodes in the reducing part of the flame (proximal and distal)... add 400 - 600 VDC polarizing voltage and modulate with your favorite tunes. Low frequency will be determined by the length of the seeded flame. Another one of those instances where bigger is better!

Heat and HV, beware

Soot laden flame will not be hot enough!!!! Soot will not give you ions... ya needs ions.

Stainless steel electrodes won't last through a single Jimmy Hendrix, cut. Best get yourself some tungsten (tig welding electrodes), they're cheap enough. Alternately you could use carbon arc gouging electrodes.

I've a very old text book (pre- 1900) on electrical machines; which credits Ben Franklin with a talking flame. Only reference I've seen to such a thing associated with ol Ben. I thought he had used all his "luck" up on the kite fiasco.