1. An audio signal decorrelator for deriving an output audio signal from an input audio signal, the audio signal decorrelator comprising: a frequency analyzer for extracting a first partial signal and a second partial signal from the input audio signal, the first partial signal being descriptive of an audio content in a first audio frequency range, the second partial signal being descriptive of an audio content in a second audio frequency range, the first audio frequency range comprising higher frequencies compared to the second audio frequency range; a modulation function generator to produce a time-variant modulation function; a partial signal modifier adapted to time-variantly modify the first partial signal in dependence on the time-variant modulation function produced by the modulation function generator, to acquire a first processed partial signal, and the second partial signal, to acquire a second processed partial signal, so that a modulation amplitude of a time variant phase shift or time variant delay applied to the first partial signal is higher than a modulation amplitude of a time variant phase shift or a time variant delay applied to the second partial signal, or to time-variantly modify only the first partial signal in dependence on the time-variant modulation function produced by the modulation function generator, so that a time variant phase shift or a time variant delay is applied to the first partial signal; and a signal combiner for combining the first processed partial signal and the second processed partial signal, or for combining the first processed partial signal and the second partial signal, to acquire an output audio signal; wherein the frequency analyzer comprises an analysis filterbank adapted to decompose the input audio signal into at least two spectral coefficients, a first spectral coefficient being descriptive of the audio content in the first audio frequency range, the first spectral coefficient forming the first partial signal, a second spectral coefficient being descriptive of the audio content in the second audio frequency range, the second spectral coefficient forming the second partial signal; the partial signal modifier is adapted to modulate a phase at least of the first spectral coefficient, to acquire the first processed partial signal, or to modulate the phase of the first spectral coefficient, to acquire the first processed partial signal, and a phase of the second spectral coefficient, to acquire a second processed partial signal; and the signal combiner comprises a synthesis filterbank adapted to combine the processed first partial signal and the second partial signal to acquire the output audio signal as a time domain signal, or to combine the processed first partial signal and the processed second partial signal to acquire the output audio signal as a time domain signal.