I am trying to explore ideas of how to automatically adjust an inductor's impedance for matching reasons from 5mH to 12mH for an audio application. A big problem is my input voltage AC signal is large, typically 300-600Vp and has different configurations to operate between 12kHz to 18kHz. My load varies somewhat with different devices but is capacitive at about 13nF. Currently I manually change out the inductance values based upon what frequency I operate at and that is a big hassle for configuration management. I would like to be able to create a single variable voltage controlled inductance device where the voltage would be controlled by the frequency of operation. The ideas I have looked at so far are 1) transformer device changing the air gap with a mechanical actuator. Haven't found any real products like this. 2)Adding impedance to a fixed inductance by varying the transconductance of a CE class A amp through the varying the bias voltage. Limited by the DC supply voltage needed because of the large AC signal. 3) Having a tapped inductor with small inductor increments and switch to choose between them. Not very smooth. 4) Roller Inductor, big and bulky, power hungry, antiquated. Any better ideas?