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
Cyclotronguy