A method of processing a pair of signals to generate modified binaural filters, the method comprising: accepting a pair of signals representing the impulse responses of a corresponding pair of to-be-matched binaural filters configured to binauralize an audio signal; processing a sum filter and difference filter representation of the pair of accepted signals by a pair of filters, characterized in that: each of the pair of filters is characterized by a modifying filter that has time varying filter characteristics, the processing forming a sum filter and difference filter representation of a pair of modified signals representing the impulse responses of a corresponding pair of modified binaural filters, the modified binaural filters are characterizable by a modified sum filter and a modified difference filter, and the time varying filters are configured such that: impulse responses of the modified sum and difference filters include a direct part defined by head related transfer functions for a listener listening to a virtual speaker at a predefined location; the modified sum filter has a shorter reverberation time compared to the modified difference filter, and there is a smooth transition from the direct part of the impulse response of the modified sum filter to a negligible response part of the modified sum filter, with smooth transition being frequency selective over time, wherein the negligible response part is where the impulse response of the modified sum filter falls below -60dB of its initial value. accepting a pair of signals representing the impulse responses of a corresponding pair of to-be-matched binaural filters configured to binauralize an audio signal; processing a sum filter and difference filter representation of the pair of accepted signals by a pair of filters, characterized in that: each of the pair of filters is characterized by a modifying filter that has time varying filter characteristics, the processing forming a sum filter and difference filter representation of a pair of modified signals representing the impulse responses of a corresponding pair of modified binaural filters, the modified binaural filters are characterizable by a modified sum filter and a modified difference filter, and the time varying filters are configured such that: impulse responses of the modified sum and difference filters include a direct part defined by head related transfer functions for a listener listening to a virtual speaker at a predefined location; the modified sum filter has a shorter reverberation time compared to the modified difference filter, and there is a smooth transition from the direct part of the impulse response of the modified sum filter to a negligible response part of the modified sum filter, with smooth transition being frequency selective over time, wherein the negligible response part is where the impulse response of the modified sum filter falls below -60dB of its initial value. each of the pair of filters is characterized by a modifying filter that has time varying filter characteristics, the processing forming a sum filter and difference filter representation of a pair of modified signals representing the impulse responses of a corresponding pair of modified binaural filters, the modified binaural filters are characterizable by a modified sum filter and a modified difference filter, and the time varying filters are configured such that: impulse responses of the modified sum and difference filters include a direct part defined by head related transfer functions for a listener listening to a virtual speaker at a predefined location; the modified sum filter has a shorter reverberation time compared to the modified difference filter, and there is a smooth transition from the direct part of the impulse response of the modified sum filter to a negligible response part of the modified sum filter, with smooth transition being frequency selective over time, wherein the negligible response part is where the impulse response of the modified sum filter falls below -60dB of its initial value. impulse responses of the modified sum and difference filters include a direct part defined by head related transfer functions for a listener listening to a virtual speaker at a predefined location; the modified sum filter has a shorter reverberation time compared to the modified difference filter, and there is a smooth transition from the direct part of the impulse response of the modified sum filter to a negligible response part of the modified sum filter, with smooth transition being frequency selective over time, wherein the negligible response part is where the impulse response of the modified sum filter falls below -60dB of its initial value.