An audio-
processing device having an audio input, for receiving audio signals, each 
audio signal having a mixture of components, each corresponding to a sound source, and a control input, for receiving, for each sound source, a desired 
gain factor associated with the source, by which it is desired to amplify the corresponding component, and an auxiliary 
signal generator, for generating at least one auxiliary 
signal from the audio signals, and with a different mixture of components as compared with a reference 
audio signal; and a scaling coefficient 
calculator, for calculating scaling coefficients based upon the desired 
gain factors and upon parameters of the different mixture, each scaling coefficient associated with one of the auxiliary 
signal and optionally the reference 
audio signal, and an 
audio synthesis unit, for synthesizing an output audio signal by applying scaling coefficients to the auxiliary signal and optionally the reference audio signal and combining the results.