An apparatus, comprising: an interface system; and a logic system configured for: receiving, via the interface system, audio reproduction data comprising one or more audio objects and associated metadata; receiving, via the interface system, reproduction environment data comprising an indication of a number of reproduction speakers of an actual three-dimensional reproduction environment and an indication of the location of each reproduction speaker within the actual reproduction environment; and rendering the one or more audio objects into one or more speaker feed signals based, at least in part, on the associated metadata, wherein each speaker feed signal corresponds to at least one of the reproduction speakers within the actual reproduction environment, characterized in that: the metadata associated with each audio object includes speaker zone constraint metadata indicating whether rendering the respective audio object involves imposing speaker zone constraints, and wherein rendering the one or more audio objects includes rendering the respective audio object by imposing speaker zone constraints in response to the speaker zone constraint metadata, and wherein rendering the one or more audio objects further includes controlling a spread of the respective audio object in one or more of three dimensions. an interface system; and a logic system configured for: receiving, via the interface system, audio reproduction data comprising one or more audio objects and associated metadata; receiving, via the interface system, reproduction environment data comprising an indication of a number of reproduction speakers of an actual three-dimensional reproduction environment and an indication of the location of each reproduction speaker within the actual reproduction environment; and rendering the one or more audio objects into one or more speaker feed signals based, at least in part, on the associated metadata, wherein each speaker feed signal corresponds to at least one of the reproduction speakers within the actual reproduction environment, characterized in that: the metadata associated with each audio object includes speaker zone constraint metadata indicating whether rendering the respective audio object involves imposing speaker zone constraints, and wherein rendering the one or more audio objects includes rendering the respective audio object by imposing speaker zone constraints in response to the speaker zone constraint metadata, and wherein rendering the one or more audio objects further includes controlling a spread of the respective audio object in one or more of three dimensions. receiving, via the interface system, audio reproduction data comprising one or more audio objects and associated metadata; receiving, via the interface system, reproduction environment data comprising an indication of a number of reproduction speakers of an actual three-dimensional reproduction environment and an indication of the location of each reproduction speaker within the actual reproduction environment; and rendering the one or more audio objects into one or more speaker feed signals based, at least in part, on the associated metadata, wherein each speaker feed signal corresponds to at least one of the reproduction speakers within the actual reproduction environment, characterized in that: the metadata associated with each audio object includes speaker zone constraint metadata indicating whether rendering the respective audio object involves imposing speaker zone constraints, and wherein rendering the one or more audio objects includes rendering the respective audio object by imposing speaker zone constraints in response to the speaker zone constraint metadata, and wherein rendering the one or more audio objects further includes controlling a spread of the respective audio object in one or more of three dimensions. the metadata associated with each audio object includes speaker zone constraint metadata indicating whether rendering the respective audio object involves imposing speaker zone constraints, and wherein rendering the one or more audio objects includes rendering the respective audio object by imposing speaker zone constraints in response to the speaker zone constraint metadata, and wherein rendering the one or more audio objects further includes controlling a spread of the respective audio object in one or more of three dimensions.