What ignitoin leads do you have and are you running resistor plug caps? If so, what value?
Resistance is placed in the ignition lead system to soften the ignition pulse. The removes the high frequency component of the spark signal to reduce radiation of electromagnetic signals from the ignition wires behaving as transmission antennas.
If you are powering your headphone driving appliance from the bike's electrical system, you may also have to filter the power input to that device, as your coils may be driving back EMF pulses into the bike's electrical system.
Cheers,