A method and an apparatus for encoding an audio signal. The apparatus includes a converter converting the audio signal into a spectral representation; a scale parameter calculator calculating scale parameters; a spectral processor processing the spectral representation using the scale parameters; and a scale parameter encoder generating an encoded representation of the scale parameters. The scale parameter calculator is calculates an amplitude-related measure for each band to obtain a set of amplitude-related measures. A pre-emphasis operation is performed to the amplitude-related measures, so that low frequency amplitudes are emphasized with respect to high frequency amplitudes according to a tilt value, or a pre-emphasis factor. The scale parameter calculator controls the tilt value, or the pre-emphasis factor, based on a harmonicity measure of the audio signal.