Olivier Messiaen's langage communicable is transmitted in three ways: in three primary sources; through performances of the three pieces in which it occurs; and in secondary material. This chapter discusses two of the most important aspects of comprehension: perception and retention. The main problems with musical perception are discussed by scientists W. Jay Dowling and Dane Harwood in their study of music cognition. The often disjunct melodic contours of the langage are not conducive to retention, nor are the timbre and dynamics the same for each phrase in the langage. Messiaen composed ten pieces after the Meditations, including the gigantic opera Saint Francois d'Assise. The rhythm is consistent with the cipher in the Meditations, the only difference being that the letters have all been given accent articulation marks, presumably as another means of emphasizing the word.