A method for i) generating spectral mapping coefficients, SMCs, in an encoding process, ii) carrying the SMCs along with an audio signal, and iii) reproducing, on a second set of channels, the audio signal present on a first set of channels using the SMCs, by: - providing, using a master source material being a multitrack source, a basic stereo or mono carrier mix, - producing a multichannel mix in a desired multichannel output format by leveling and equalizing each track of the multitrack source so that during the multichannel mixing, the level and equalization of the master source tracks are i) maintained the same as in the carrier mix and ii) are panned to produce the desired multichannel mix by directing different amounts of the multitrack source tracks to different channels, and analog/digital multiplexing the multichannel mix so as to act as a guide for determining the SMCs in the encoding process, and - distributing the level adjusted and equalized track signals among the carrier channels and analog/digital multiplexing the distributed level-adjusted and equalized carrier channels, - spectrally decomposing (64, 66) the multichannel mix and the carrier mix into the same spectral bands, - dividing a signal level in each band of each input multichannel mix by the signal level in the corresponding band of the carrier mix to determine the value of the corresponding SMC, and - formatting the SMCs so as to output a spectral mapping data stream, wherein the method comprises: receiving said audio signal organized into successive temporal aperture periods on multiple spectral bands of said first set of channels along with a set of the SMCs, wherein the set of SMCs are usable to, for the spectral bands of each of the aperture periods in each channel in said first set, map the audio signal levels on the spectral bands in said channel on to corresponding spectral bands in each of said second set of channels, reading said audio signal on said first set of channels and said SMCs, decomposing the audio signal into spectral components according to the spectral bands in said first set of channels, and applying said SMCs to said audio signal spectral components on the spectral bands in said first set of channels to obtain the audio signal on said second set of channels (5, 9). - providing, using a master source material being a multitrack source, a basic stereo or mono carrier mix, - producing a multichannel mix in a desired multichannel output format by leveling and equalizing each track of the multitrack source so that during the multichannel mixing, the level and equalization of the master source tracks are i) maintained the same as in the carrier mix and ii) are panned to produce the desired multichannel mix by directing different amounts of the multitrack source tracks to different channels, and analog/digital multiplexing the multichannel mix so as to act as a guide for determining the SMCs in the encoding process, and - distributing the level adjusted and equalized track signals among the carrier channels and analog/digital multiplexing the distributed level-adjusted and equalized carrier channels, - spectrally decomposing (64, 66) the multichannel mix and the carrier mix into the same spectral bands, - dividing a signal level in each band of each input multichannel mix by the signal level in the corresponding band of the carrier mix to determine the value of the corresponding SMC, and - formatting the SMCs so as to output a spectral mapping data stream, wherein the method comprises: receiving said audio signal organized into successive temporal aperture periods on multiple spectral bands of said first set of channels along with a set of the SMCs, wherein the set of SMCs are usable to, for the spectral bands of each of the aperture periods in each channel in said first set, map the audio signal levels on the spectral bands in said channel on to corresponding spectral bands in each of said second set of channels, reading said audio signal on said first set of channels and said SMCs, decomposing the audio signal into spectral components according to the spectral bands in said first set of channels, and applying said SMCs to said audio signal spectral components on the spectral bands in said first set of channels to obtain the audio signal on said second set of channels (5, 9). receiving said audio signal organized into successive temporal aperture periods on multiple spectral bands of said first set of channels along with a set of the SMCs, wherein the set of SMCs are usable to, for the spectral bands of each of the aperture periods in each channel in said first set, map the audio signal levels on the spectral bands in said channel on to corresponding spectral bands in each of said second set of channels, reading said audio signal on said first set of channels and said SMCs, decomposing the audio signal into spectral components according to the spectral bands in said first set of channels, and applying said SMCs to said audio signal spectral components on the spectral bands in said first set of channels to obtain the audio signal on said second set of channels (5, 9).