A method for separating an audio signal into a harmonic signal component and a transient signal component is disclosed. The method includes the steps of: transferring the audio signal into a frequency space in order to obtain a transferred audio signal in dependence on frequency and time and applying a non-linear smoothing filter to the transferred audio signal over frequency to obtain a filtered transient signal in which the harmonic signal component is suppressed relative to the transient signal component. The method further includes applying the non-linear smoothing filter to the transferred audio signal over time to obtain a filtered harmonic signal in which the transient signal component is suppressed relative to the harmonic signal component and determining the harmonic signal component and the transient signal component based on the filtered harmonic signal and the filtered transient signal.