A method of periodically compensating a response of a keyboard, the keyboard comprising a plurality of keys each having a key sensor, wherein each key sensor comprises an active resonant circuit, a passive tuned resonant circuit and a detector, the method comprising: retrieving from storage a detected initial output signal, O t0, of an initial key sensor, K 0, of the plurality of key sensors, wherein the detected initial output signal O t0 corresponds to an output signal of said initial key sensor K 0 detected at a first time, t o, wherein at t 0 an active resonant circuit of said initial key sensor K 0 is being driven at a frequency below a resonant frequency of said active resonant circuit of said initial key sensor K 0; and periodically, for at least one key sensor of the plurality of key sensors: detecting a later output signal, O t1, of said at least one key sensor at a time after t 0; calculating an adjustment value, wherein the adjustment value is a difference between the initial output signal O t0 and the later output signal On; and compensating the response of the keyboard by adjusting an operational output of said at least one key sensor using the adjustment value, where the operational output is an output from said at least one key sensor when the active resonant circuit of said at least one key sensor is being driven at the resonant frequency of the active resonant circuit of said at least one key sensor. retrieving from storage a detected initial output signal, O t0, of an initial key sensor, K 0, of the plurality of key sensors, wherein the detected initial output signal O t0 corresponds to an output signal of said initial key sensor K 0 detected at a first time, t o, wherein at t 0 an active resonant circuit of said initial key sensor K 0 is being driven at a frequency below a resonant frequency of said active resonant circuit of said initial key sensor K 0; and periodically, for at least one key sensor of the plurality of key sensors: detecting a later output signal, O t1, of said at least one key sensor at a time after t 0; calculating an adjustment value, wherein the adjustment value is a difference between the initial output signal O t0 and the later output signal On; and compensating the response of the keyboard by adjusting an operational output of said at least one key sensor using the adjustment value, where the operational output is an output from said at least one key sensor when the active resonant circuit of said at least one key sensor is being driven at the resonant frequency of the active resonant circuit of said at least one key sensor. detecting a later output signal, O t1, of said at least one key sensor at a time after t 0; calculating an adjustment value, wherein the adjustment value is a difference between the initial output signal O t0 and the later output signal On; and compensating the response of the keyboard by adjusting an operational output of said at least one key sensor using the adjustment value, where the operational output is an output from said at least one key sensor when the active resonant circuit of said at least one key sensor is being driven at the resonant frequency of the active resonant circuit of said at least one key sensor.