Abstract: The method is provided for simulating an audio effect processor. At least two impulse responses are stored representing the audio processor for input signals having different characteristics. The same characteristic of the input signal is then repeatedly assessed and at least one of the impulse responses selected to apply to the input signal in dependence on the result of the assessment. The selected impulse response is then applied to the input signal to derive an output signal. This process continues throughout the duration of the input signal, thereby taking account of time dependent changes in the assessed characteristics.