1. A method implemented by one or more computing devices, the method comprising: receiving a sound signal originated by one or more sound sources; fitting a universal audio model having a collection of individual models of sound sources to sound data associated with the sound signal, the fitting performed by selecting from the models in the collection based on correspondence of the sound data to respective said models, wherein the selecting is performed based on a penalty that encourages the correspondence and use of fewer of models in instances of strong correspondence between a subset of the models and the sound data as opposed to instances of weak correspondence between the subset of the models and the sound data; and decomposing the sound data using the selected models of the universal audio model.