In an apparatus for creating musical performance data according to operations of a user, a screen display section displays an input screen having a data input area for use in inputting of musical performance data. A position indication section operates when a first operation is taken by the user for indicating a desired position on the data input area. A display enlargement section operates when a second operation is taken eventually by the user for enlarging a local portion of the data input area around the indicated position and displaying the enlarged local portion over the data input area, thereby allowing the user to take a supplemental first operation on the enlarged local portion more easily than the first operation such that the position indication section responds to the supplemental first operation for indicating a desired position on the enlarged local portion of the data input area. A data input section is responsive to a third operation of the user for inputting musical performance data corresponding to the position indicated by the first operation when the supplemental first operation is not taken by the user, or corresponding to the position indicated by the supplemental first operation when the supplemental first operation is taken by the user.