Machine composer for adapting pitch succession to musical background

To provide a machine composer capable of efficiently composing natural melodies with a simplified system configuration and without requiring complicated data processing: A melody material storage 10 stores a plurality of melody materials each represented by a plurality of note records. Each note record in a melody material contains data items of pitch and note type or function. Thus, pitches of the plurality of note records constitute an original pitch succession whereas note types of the records define an original note type succession. A note type of each note record represents a pitch function specified by musical background of the original pitch succession. A input device 20 enters musical background information (including for example keynote, scale and chord). A pitch adapter 30 successively makes adapted pitches based on the entered musical background information and based on pitch and note type data from the melody material storage 10 to thereby compose a musical pitch succession or melody that is adapted to the entered musical background and depends on the original pitch and note type succession.