A musical piece recommendation system that allows instantaneous registration of a new user and a new musical piece without retraining in a basic training section. A first incremental training section monitors a rating history storage section, and each time a change is made to a rating history or a new user is added, performs updating of or addition of the topic selection probability for the user for which the change is made to the rating history or for the new user such that the likelihood determined by a basic training section is kept maximized. A second incremental training section monitors an acoustic feature storage section, and each time a new musical piece is added to perform addition to acoustic features, adds the musical piece selection probability related to the added musical piece such that the likelihood determined by the basic training section is kept maximized.