Audio Signal Synthesizer and Audio Signal Encoder

In accordance with a first aspect of the invention, an audio signal synthesizer generates a synthesis audio signal having a first frequency band and a second synthesized frequency band derived from the first frequency band. The audio signal synthesizer comprises a patch generator, a spectral converter, a raw signal processor and a combiner. The patch generator performs at least two different patching algorithms, wherein each patching algorithm generates a raw signal having signal components in the second synthesized frequency band using an audio signal having signal components in the first frequency band. The patch generator is adapted to select one of the at least two different patching algorithms in response to a control information for a first time portion and the other of the at least two different patching algorithms in response to the control information for a second time portion different from the first time portion to obtain the raw signal for the first and the second time portion. The spectral converter converts the raw signal into a raw signal spectral representation. The raw signal processor processes the raw signal spectral representation in response to spectral domain spectral band replication parameters to obtain an adjusted raw signal spectral representation. The combiner combines an audio signal having signal components in the first band or a signal derived from the audio signal with the adjusted raw signal spectral representation or with a further signal derived from the adjusted raw signal spectral representation to obtain the synthesis audio signal.