135 which is configured to decode the audio signals to obtain the downmix signals. Similarly the decoder/demultiplexer 133 may comprise a metadata extractor 137 which is configured to receive the encoded metadata and generate metadata. The decoder/demultiplexer 133 can in some embodiments be a computer (running suitable software stored on memory and on at least one processor), or alternatively a specific device utilizing, for example, FPGAs or ASICs. The decoded metadata and downmix audio signals may be passed to a synthesis processor 139. The system 100 ‘synthesis’ part 13 1 further shows a synthesis processor 139 configured to receive the downmix and the metadata and re-creates in any suitable format a synthesized spatial audio in the form of multi-channel signals 110 (these may be multichannel loudspeaker format or in some embodiments any suitable output format such as binaural or Ambisonics signals, depending on the use case) based on the downmix signals and the metadata. Therefore in summary first the system (analysis part) is configured to receive multi-channel audio signals. Then the system (analysis part) is configured to generate a downmix or otherwise generate a suitable transport audio signal (for example by selecting some of the audio signal channels). The system is then configured to encode for storage/transmission the downmix (or more generally the transport) signal and. After this the system may store/transmit the encoded downmix and metadata. The system may retrieve/receive the encoded downmix and metadata. Then the system is configured to extract the downmix and metadata from encoded downmix and metadata parameters, for example demultiplex and decode the encoded downmix and metadata parameters. The system (synthesis part) is configured to synthesize an output multi- channel audio signal based on extracted downmix of multi-channel audio signals and metadata.