The publication of the first edition of the
Graduale simplex was achieved in 1967, as a reworking of the Gregorian chant book in order to satisfy the
Sacrosanctum Concilium Constitution of 4 December 1963, following the Second Vatican Council. {{Quote|The typical edition of the books of Gregorian chant is to be completed; and a more critical edition is to be prepared of those books already published since the restoration by St. Pius X. It is desirable also that an edition be prepared containing simpler melodies, for use in small churches. == History ==