Abstract: A radio receiver is effective to receive a radio frequency signal and derive therefrom a standard stereo composite signal comprising a sum of channels signal having components within a first band of frequencies in the audio range and a difference of channels signal having components within a second band of frequencies above the first band of frequencies. The radio receiver is provided with a low pass filter having a high frequency roll-off characteristic within the first frequency band and a substantially flat attenuated amplitude characteristic across the second frequency band. Linear mixer apparatus mixes filtered and unfiltered stereo composite signals in controlled relative proportion responsive to a control signal to produce a modified stereo composite signal for application to stereo decoder apparatus in order to simultaneously roll-off the high frequencies in each derived channel and to attenuate the difference of channels signal in degree controlled by the control signal.