Relationship to Other Chapters

Chapter XVII directly extends the theoretical foundation established in Chapter XVI, demonstrating practical applications of the modes in contexts requiring tonal orientation or modal variety. The mixing of modes with major tonality connects to discussions of added notes (Chapter XIII) and special chords (Chapter XIV), showing how modal and tonal materials can be combined within single passages. The modulation techniques relate to the "list of connections of chords" in Chapter XIV, paragraph 8, providing additional strategies for harmonic progression. The chapter anticipates Chapter XVIII's discussion of the modes' relationship to various contemporary harmonic systems (modal, atonal, polytonal) and Chapter XIX's systematic treatment of polymodality, where multiple modes operate simultaneously. References to le Banquet céleste (Example 363) and Les Offrandes oubliées (Example 137) demonstrate how these modulation techniques function in actual compositions. The flexibility demonstrated here—modes as both autonomous systems and elements within tonal contexts—reflects the broader aesthetic principle articulated in Chapter I, where Messiaen advocates for technical resources that serve rather than dictate expressive intentions.