Low bit-rate audio encoding

In a sinusoidal audio encoder a number of sinusoids are estimated per audio segment. A sinusoid is represented by frequency, amplitude and phase. The invention uses a track dependent quantization of phase. A track is encoded with a suitable initial (e.g. frequency dependent) quantization grid that is chosen among a set of possible initial grids that may vary from fine to coarse. If, in a series of time segments the frequency variation in a particular track is smaller than a predetermined value, the track is quantized using a finer quantization grid. The invention gives a significant improvement in decoded signal quality, especially for low bit-rate quantizers.