Prolation Prolation Prolation is a term used in the theory of the mensural notation of medieval and Renaissance music to describe its rhythmic structure on a small scale, as opposed to "tempus", which described a larger scale. The term "prolation" is derived from the Latin "prolatio", first used by Philippe de Vitry in describing Ars Nova, a musical style that came about in 14th-century France. Prolation, together with tempus, corresponds roughly to the concept of time signature in modern music. Prolation describes whether a semibreve (whole note) is equal in length to two minims (half notes) ("minor prolation" or "imperfect prolation";
Clavier-Übung III we trust, Protect Christ's congregation, His everlasting truth assert, All evil graciously avert, Lead us to life eternal.</poem> BWV 675, 66 bars long, is a two-part invention for the upper and lower voices with the "cantus firmus" in the alto part. The two outer parts are intricate and rhythmically complex with wide leaps, contrasting with the "cantus firmus" which moves smoothly by steps in minims and crotchets. The time signature has been taken to be one of the references in this movement to the Trinity. Like the two preceding chorale preludes, there is no explicit "manualiter" marking, only an ambiguous