Olivier Messiaen's langage uses the roman alphabet and a reductive combination of the syntax and grammar of French and Latin, which makes its classification straightforward. Application of linguistic theory helps to identify exactly how the langage works and points out the limitations of its use. This chapter presents a brief discussion of three broad categories of leitmotifs: 'representational', 'langage' and 'associated'. One of the most striking features of Messiaen's musical alphabet is the wide tessitura of the pitches, which range from D1 to F#6. Grammar is the term applied to the overall linguistic structure of language, including phonology, morphology, syntax and semantics, as well as to any systematic account of the structure of a language. Messiaen's leitmotifs constitute a sophisticated system, in the traditional Wagnerian sense, in which a musical figure is used to represent a being or idea.