A multi-band signal processor comprising: a signal input for receipt of a digital audio input signal (x(n)), a cascade of digital all-pass filters configured for receipt of the digital audio input signal and generation of M delayed digital audio signal samples (p 0 (n) - p K (n)) at respective tapping nodes interposed between the digital all-pass filters, a signal convolution processor configured for convolving the M delayed digital audio signal samples (p 0 (n) - p K (n)) with M time-varying filter coefficients (g 1 - g M) of a processing filter to produce a processed digital output signal (y(n)), a frequency domain transform processor configured for converting the M delayed digital audio signal samples (p 0 (n) - p K (n)) to frequency domain representation to produce respective signal spectrum values in a predetermined number of frequency bands, N, a level estimator configured to compute respective signal level estimates in the predetermined number of frequency bands based on the respective signal spectrum values, a processing gain calculator configured for computation of a frequency domain gain coefficient (G k) for each of the predetermined number of frequency bands based on the respective signal level estimates and band gain laws, an inverse frequency domain transform processor configured for conversion of the N frequency domain gain coefficients (G k) into the M time-varying filter coefficients (g 1 - g M) of the processing filter wherein each of M and N is a positive integer number; and characterised in that the frequency domain transform processor is configured to compute signal spectrum values of at least two different frequency bands at different band update rates. a signal input for receipt of a digital audio input signal (x(n)), a cascade of digital all-pass filters configured for receipt of the digital audio input signal and generation of M delayed digital audio signal samples (p 0 (n) - p K (n)) at respective tapping nodes interposed between the digital all-pass filters, a signal convolution processor configured for convolving the M delayed digital audio signal samples (p 0 (n) - p K (n)) with M time-varying filter coefficients (g 1 - g M) of a processing filter to produce a processed digital output signal (y(n)), a frequency domain transform processor configured for converting the M delayed digital audio signal samples (p 0 (n) - p K (n)) to frequency domain representation to produce respective signal spectrum values in a predetermined number of frequency bands, N, a level estimator configured to compute respective signal level estimates in the predetermined number of frequency bands based on the respective signal spectrum values, a processing gain calculator configured for computation of a frequency domain gain coefficient (G k) for each of the predetermined number of frequency bands based on the respective signal level estimates and band gain laws, an inverse frequency domain transform processor configured for conversion of the N frequency domain gain coefficients (G k) into the M time-varying filter coefficients (g 1 - g M) of the processing filter wherein each of M and N is a positive integer number; and characterised in that the frequency domain transform processor is configured to compute signal spectrum values of at least two different frequency bands at different band update rates.