A Multi-channel synthesiser for generating at least three output channels (110, 111, 112) using an input signal having at least one base channel, the base channel being derived from the original multi-channel signal (101, 102, 103), the input signal further including at least two different up-mixing parameters, and an up-mixer mode indication (1005) indicating, in a first state that a first up-mixing rule is to be performed, and, indicating, in a second state, that a different second up-mixing rule is to be performed, uses an up-mixer for up-mixing the at least one base channel using the at least two different up-mixing parameters based on the first or the second up-mixing rule in response to the up-mixer mode indication (1005) so that the at least three output channels (110, 111, 112) are obtained.