A device comprising: a receiver configured to receive a first inter-channel prediction gain parameter, a second inter-channel prediction gain parameter, and an encoded audio signal, wherein the encoded audio signal comprises an encoded mid signal; and a decoder configured to: generate a synthesized mid signal based on the encoded mid signal; process the synthesized mid signal to generate a low-band synthesized mid signal and a high-band synthesized mid signal; generate a low-band intermediate synthesized side signal based on the low-band synthesized mid signal and the first inter-channel prediction gain parameter; and generate a high-band intermediate synthesized side signal based on the high-band synthesized mid signal and the second inter-channel prediction gain parameter; generate a synthesized side signal, characterised in that generating the synthesized side signal comprises: filtering the low-band intermediate synthesized side signal using an all-pass filter to generate a first synthesized side signal; adjusting at least one parameter of at least one of multiple stages of the all-pass filter; filtering the high-band intermediate synthesized side signal using the adjusted all-pass filter to generate a second synthesized side signal; and combining the first synthesized side signal and the second synthesized side signal to generate the synthesized side signal. a receiver configured to receive a first inter-channel prediction gain parameter, a second inter-channel prediction gain parameter, and an encoded audio signal, wherein the encoded audio signal comprises an encoded mid signal; and a decoder configured to: generate a synthesized mid signal based on the encoded mid signal; process the synthesized mid signal to generate a low-band synthesized mid signal and a high-band synthesized mid signal; generate a low-band intermediate synthesized side signal based on the low-band synthesized mid signal and the first inter-channel prediction gain parameter; and generate a high-band intermediate synthesized side signal based on the high-band synthesized mid signal and the second inter-channel prediction gain parameter; generate a synthesized side signal, characterised in that generating the synthesized side signal comprises: filtering the low-band intermediate synthesized side signal using an all-pass filter to generate a first synthesized side signal; adjusting at least one parameter of at least one of multiple stages of the all-pass filter; filtering the high-band intermediate synthesized side signal using the adjusted all-pass filter to generate a second synthesized side signal; and combining the first synthesized side signal and the second synthesized side signal to generate the synthesized side signal. generate a synthesized mid signal based on the encoded mid signal; process the synthesized mid signal to generate a low-band synthesized mid signal and a high-band synthesized mid signal; generate a low-band intermediate synthesized side signal based on the low-band synthesized mid signal and the first inter-channel prediction gain parameter; and generate a high-band intermediate synthesized side signal based on the high-band synthesized mid signal and the second inter-channel prediction gain parameter; generate a synthesized side signal, characterised in that generating the synthesized side signal comprises: filtering the low-band intermediate synthesized side signal using an all-pass filter to generate a first synthesized side signal; adjusting at least one parameter of at least one of multiple stages of the all-pass filter; filtering the high-band intermediate synthesized side signal using the adjusted all-pass filter to generate a second synthesized side signal; and combining the first synthesized side signal and the second synthesized side signal to generate the synthesized side signal. filtering the low-band intermediate synthesized side signal using an all-pass filter to generate a first synthesized side signal; adjusting at least one parameter of at least one of multiple stages of the all-pass filter; filtering the high-band intermediate synthesized side signal using the adjusted all-pass filter to generate a second synthesized side signal; and combining the first synthesized side signal and the second synthesized side signal to generate the synthesized side signal.