Example embodiments disclosed herein relate to audio signal processing. The audio signal has multiple audio objects. A method of processing an audio signal is disclosed. The method includes obtaining an object position for each of the audio objects; and determining cluster positions for grouping the audio objects into clusters based on the object positions, a plurality of object-to-cluster gains, and a set of metrics. The metrics indicate a quality of the cluster positions and a quality of the object-to-cluster gains, each of the cluster positions is a centroid of a respective one of the clusters, and one of the object-to-cluster gains defines a ratio of the respective audio object in one of the clusters. The method also includes determining the object-to-cluster gains based on the object positions, the cluster positions and the set of metrics; and generating a cluster signal based on the determined cluster positions and object-to-cluster gains. Corresponding system and computer program product are also disclosed.