Summary

Chapter XI systematizes small-scale formal organization through three fundamental sentence types: song-sentence (antecedent-consequent-middle-final creating ABA' structure), binary sentence (theme-commentary-theme-commentary creating ABAB' alternation), and ternary sentence (theme-consequent-commentary-consequent-theme-consequent creating symmetrical arch form). By defining commentary as melodic development varying theme fragments rhythmically, melodically, and harmonically, Messiaen establishes how developmental procedures from Chapter X organize into complete formal units. The extensive catalog of melodic periods (Examples 138–150) demonstrates his synthetic method—drawing from medieval trouvères, Baroque masters, Classical and Romantic composers, early 20th-century modernists, non-Western traditions, and natural sources, then transforming all material through the "deforming prism" of his personal language to create periods that unite "fantasy and research" while destroying resemblance to their models. This chapter bridges local melodic construction (Chapters VIII–X) and large-scale forms (Chapter XII), showing how phrases organize into sentences that become building blocks for complete movements.

For contemporary readers, this chapter illustrates how traditional formal thinking—period structures, antecedent-consequent relationships, developmental sections—can be adapted to non-tonal compositional systems organized through modal collections and rhythmic techniques rather than functional harmony. Messiaen's formal approach maintains hierarchical organization (phrase-period-sentence) while operating within parametric systems (modes of limited transposition, added values, nonretrogradable rhythms) that replace tonal function. The invocation of d'Indy and Dupré positions this work within French pedagogical tradition, demonstrating that innovation builds upon systematic training rather than rejecting it. The chapter's conclusion—that all borrowings receive "different blood, unexpected melodic and rhythmic color" through transformation—articulates Messiaen's aesthetic of synthesis: maximum stylistic diversity unified through personal compositional voice, creating music simultaneously historical (acknowledging sources) and original (transforming them beyond recognition).