It is argued that purely perceptual or generative accounts of music are inadequate to account for its specificity, and that proper accounts of music must take into account also a more fundamental level of the mind (or of consciousness), a level we term the "aesthetic subsystem". The latter constitutes a domain of universality and of meaning that acts in conjunction with more peripheral aspects of cognition. Suggestive parallels with systems such as biosystems and lasers are used to account for a number of features of musical processes in terms of the model.