A scale information inputting section receives an input of scale information of a musical composition. Based on the scale information of the musical composition inputted to the scale information inputting section, an appearance probability calculating section calculates appearance probabilities of pitch names included in the scale information for each of the pitch names. A template storing section stores 24 types of previously created templates respectively corresponding to 24 types of keys. Based on an appearance probability distribution of the musical composition calculated by the appearance probability calculating section and each of the templates stored in the template storing section, a load ratio calculating section calculates load ratios respectively corresponding to the templates. A tonal information detecting section detects, as tonal information of the musical composition, information indicating the load ratios calculated by the load ratio calculating section as a set, or information calculated based on the set of the load ratios.