Apparatus for decoding a previous encoded multichannel signal of a previous frame to obtain three or more previous audio output channels, and for decoding a current encoded multichannel signal of a current frame to obtain three or more current audio output channels, wherein the apparatus is configured to receive the current encoded multichannel signal, and to receive side information comprising first multichannel parameters (MCH_PAR2), wherein the apparatus is configured to decode the current encoded multichannel signal of the current frame to obtain a set of three or more decoded channels (D1, D2, D3) of the current frame, wherein the apparatus is configured to select a first selected pair of two decoded channels (D1, D2) from the set of three or more decoded channels (D1, D2, D3) identified by the first multichannel parameters (MCH_PAR2), wherein the apparatus is configured to generate a first group of two or more processed channels (P1*,P2*) based on said first selected pair of two decoded channels (D1, D2) to obtain an updated set of three or more decoded channels (D3, P1*, P2*), characterized in that, before the apparatus generates the first group of two or more processed channels (P1*,P2*) based on said first selected pair of two decoded channels (D1, D2), the apparatus is configured to identify for at least one of the two channels of said first selected pair of two decoded channels (D1, D2), one or more frequency bands, within which all spectral lines are quantized to zero, and to generate a mixing channel using two or more, but not all of the three or more previous audio output channels, and to fill the spectral lines of the one or more frequency bands, within which all spectral lines are quantized to zero, with noise generated using spectral lines of the mixing channel, wherein the apparatus is configured to select the two or more previous audio output channels that are used for generating the mixing channel from the three or more previous audio output channels depending on the side information. wherein the apparatus is configured to receive the current encoded multichannel signal, and to receive side information comprising first multichannel parameters (MCH_PAR2), wherein the apparatus is configured to decode the current encoded multichannel signal of the current frame to obtain a set of three or more decoded channels (D1, D2, D3) of the current frame, wherein the apparatus is configured to select a first selected pair of two decoded channels (D1, D2) from the set of three or more decoded channels (D1, D2, D3) identified by the first multichannel parameters (MCH_PAR2), wherein the apparatus is configured to generate a first group of two or more processed channels (P1*,P2*) based on said first selected pair of two decoded channels (D1, D2) to obtain an updated set of three or more decoded channels (D3, P1*, P2*), characterized in that, before the apparatus generates the first group of two or more processed channels (P1*,P2*) based on said first selected pair of two decoded channels (D1, D2), the apparatus is configured to identify for at least one of the two channels of said first selected pair of two decoded channels (D1, D2), one or more frequency bands, within which all spectral lines are quantized to zero, and to generate a mixing channel using two or more, but not all of the three or more previous audio output channels, and to fill the spectral lines of the one or more frequency bands, within which all spectral lines are quantized to zero, with noise generated using spectral lines of the mixing channel, wherein the apparatus is configured to select the two or more previous audio output channels that are used for generating the mixing channel from the three or more previous audio output channels depending on the side information.