For each section forming a music piece, music template information is supplied which includes at least information indicative of a pitch variation tendency in the section. A plurality of already-composed music pieces are preferably analyzed to store a plurality of pieces of such music template information so that any users can select from the stored pieces of music template information. For a music piece to be composed, the user enters information indicative of a tendency relating to the number of notes, such as syllable information of desired words or scat words, in each section of the music piece. On the basis of one of the pieces of music template information supplied and the user-entered information indicative of the number-of-notes tendency (syllable information), the length and pitch of notes in each section can be determined, which permits automatic generation of music piece data. If the music template information is used with no modification, an automatically composed music piece will considerably resemble its original music piece. The user can freely modify the music template information to be used, so that a music piece different from its corresponding original music piece can be created with the user's intention reflected thereon. The music template information can be easily modified by any users having poor knowledge of composition, and the present composing technique can be easily used by everyone.