An audio system comprises a receiver which receives an input audio signal. A decomposer (103) decomposes the audio signal into at least a transient component signal and a non-transient component signal. An output circuit (105, 107, 109) then generates a first output audio signal in response to a weighted combination of the transient component signal and the non-transient component signal. In the combination the weighting of the transient component signal is different than the weighting of the non-transient component signal. A new signal with different emphasis of specific sound characteristics can be achieved. The approach may be particularly suited to generation of new spatial audio channels from an existing spatial audio channel, such as in particular the generation of an elevated channel from audio signals of a lower channel.