1. A device for generating a complex audio spectral representation of a discrete-time audio signal, comprising: a generator for generating a block-wise real-valued audio spectral representation of the discrete-time audio signal, the audio spectral representation comprising temporally successive blocks, each block comprising a set of real audio spectral coefficients; and a post-processor for post-processing the block-wise real-valued audio spectral representation to obtain a block-wise complex approximated audio spectral representation comprising successive blocks wherein the complex approximated audio spectral representation represents the discrete-time audio signal, each block comprising a set of complex approximated audio spectral coefficients, wherein a complex approximated audio spectral coefficient can be represented by a first partial audio spectral coefficient and a second partial audio spectral coefficient, wherein at least one of the first and the second partial audio spectral coefficients is to be determined by combining at least two temporally and/or frequency-adjacent real audio spectral coefficients.