Low bit rate audio encoding and decoding in which multiple channels are represented by fewer channels and auxiliary information.

MULTIPLE CHANNELS OF AUDIO ARE COMBINED EITHER TO A MONOPHONIC COMPOSITE SIGNAL OR TO MULTIPLE CHANNELS OF AUDIO ALONG WITH RELATED AUXILIARY INFORMATION FROM WHICH MULTIPLE CHANNELS OF AUDIO ARE RECONSTRUCTED, INCLUDING IMPROVED DOWNMIXING OF MULTIPLE AUDIO CHANNELS TO A MONOPHONIC AUDIO SIGNAL OR TO MULTIPLE AUDIO CHANNELS AND IMPROVED DECORRELATION OF MULTIPLE AUDIO CHANNELS DERIVED FROM A MONOPHONIC AUDIO CHANNEL OR FROM MULTIPLE AUDIO CHANNELS. ASPECTS OF THE DISCLOSED INVENTION ARE USABLE IN AUDIO ENCODERS, DECODERS, ENCODE/DECODE SYSTEMS, DOWNMIXERS, UPMIXERS, AND DECORRELATORS,