A musical tone signal-generating apparatus which is capable of easily reflecting user's settings on the apparatus based on user's usage data by a simple operation using a portable storage medium storing the user's usage data customized on a user-by-user basis. A server, which stores users' usage data concerning use of the apparatus, on a user-by-user basis. The user's usage data concerning the use of the musical tone signal-generating apparatus by a user is read from and written into a portable storage medium. When mounting of the storage medium in said reading and writing device is detected, the users' usage data associated with the user stored in the server and the user's usage data stored in the storage medium are compared to determine which is a newer one. The newer one of the users' usage data associated with the user stored in the server and the user's usage data stored in the storage medium is enabled, based on a result of the comparison.