  Driven by the term "the arrow of time" as a general topic, the article
develops a musical discussion by referring to the etymological origin of the
term: philosophy (epistemology) and physics (thermodynamics). In particular,
the article explores two specific conditions: distinguishability and unique
orientability, from which the article derives respective musical propositions
and case studies. For the distinguishability condition, the article focuses on
the "recurrence" in music and tries to interpret Bach's Christmas Oratorio from
the perspective of "birth/resurrection". For the unique orientability
condition, the article discusses the process of delaying the climax, thereby
proposing "AB-AAB left-replication" model, implying an organicist view by
treating the temporal structure of music (e.g. form) as the product of a
dynamic process: organic growth.
