ChordLeadSheet object is the model of the Chord leadsheet editor. It holds the sections and the chord symbols.SongStructure object is the model of the Song structure editor. It holds the SongParts, each one being linked to a parent section, and each one defining a set of RhythmParameter values.SongStructure and the ChordLeadSheet will give you the "unrolled" chord lead sheet for which the backing track must be generated.Song. It is mainly used by the framework to control the Midi output device. Your MusicGenerator will use it only to retrieve the Midi channel associated to a Rhythm track (RhythmVoice).MusicGenerator: