1. An audio signal decoder for providing an upmix signal representation on the basis of a downmix signal representation and an object-related parametric information, and depending on a rendering information, the apparatus comprising: an object parameter determinator configured to acquire inter-object-correlation values for a plurality of pairs of audio objects, wherein the object parameter determinator is configured to evaluate a bitstream signaling parameter in order to decide whether to evaluate individual inter-object-correlation bitstream parameter values, to acquire inter-object-correlation values for a plurality of pairs of related audio objects, or to acquire inter-object-correlation values for a plurality of pairs of related audio objects using a common inter-object-correlation bitstream parameter value; and a signal processor configured to acquire the upmix signal representation on the basis of the downmix signal representation and using the inter-object-correlation values for a plurality of pairs of related audio objects and the rendering information; wherein the audio signal decoder is configured to combine an inter-object-correlation value IOC i,j associated with a pair of related audio objects with an object level difference value OLD i describing an object level of a first audio object of the pair of related audio objects and with an object level difference value OLD j describing an object level of a second audio object of the pair of related audio objects, to acquire a covariance value associated with the pair of related audio objects; wherein the audio decoder is configured to acquire an element e i,j of a covariance matrix according to e i,j =√{square root over (OLD i OLD j )}IOC i,j , wherein the object-related parametric information comprises the bitstream signaling parameter and the individual inter-object-correlation bitstream parameter values or the common inter-object-correlation bitstream parameter value.