“Olivier Messiaen (1908-1992) is known for his unique composition style. Incorporating complex rhythms, harmony and melodies, Meditations on the Mystery of the Holy Trinity is no exception to the composer's popular, distinctive style. Composed in 1969, Meditations on the Mystery of the Holy Trinity is an example of Messiaen's use of Serialism. The composer first used what he called his ”“musical alphabet”“ in Meditations on the Mystery of the Holy Trinity, where the alphabet includes motifs for the concepts, 'to have', 'to be' and 'God'. Furthermore, 'sentences' depict the writings of St. Thomas Aquinas. Messiaen's ”“musical alphabet”“, which he also described as ”“communicable language”“ is explained as a preface to the composition Meditations on the Mystery of the Holy Trinity. Divided into nine sections ('meditations'), a typical performance lasts about 74 minutes. Messiaen's Meditations on the Mystery of the Holy Trinity is essential to all advanced, virtuoso and contemporary organists seeking to expand and vary their repertoire.”