Spatially mixing audio signals is known in the audio arts and it is further known to mix new background sounds to a foreground sound.  There is a challenge when the new background sound is mixed with a foreground sound from a moving source.  If not carefully done the new background sound can obscure portions of the foreground sound.  The background sound is referred to as a spatial audio signal and the foreground sound is referred to as a sound object.  The key is to mix the spatial audio signal to the sound object in such a manner that the listener of the mixed result can still perceive the audio object, can perceive it as moving, and the addition of the spatial audio signal enhances the overall audio experience.  Simply mixing different audio objects on a new ambiance does not guarantee that the objects will be well audible throughout the entire recording at different spatial locations because some elements of the background ambiance may mask some of the objects. 
It is known for a recording device to transmit or otherwise provide the orientation information for the spatial audio so that the receiving device could optimize sound reproduction by knowing such captured orientation information.  But this can be improved upon and embodiments of these teachings provide a way to intelligently spatially mix sound objects to a new background ambiance by analyzing the background ambiance and automatically finding suitable spatiotemporal locations where to mix new sound objects.