In addition to the current observance of the Octave of the Immaculate Conception with Simplex rank, we also propose that the following octaves be likewise observed:
Octave of S. Stephen, Protomartyr
Octave of S. John, Apostle & Evangelist
Octave of the Holy Innocents
Octave of the Solemnity of S. Joseph
Octave of S. John the Baptist
Octave of S. Lawrence, Deacon & Martyr
Octave of the Nativity of the BVM
The Simplex Octave is to be observed thus:
* All Dies infra Octavam are ranked Simplex and follow the usual rules governing Simplex feasts, i.e. only First Vespers, precedence over Feriae per Annum but yielding to major Feriae in Advent. These days are always commemorated at both Vespers and Lauds of a higher ranking Office, unless the Office is of a Duplex I or II Class feast in which case commemorations of most octaves are generally omitted.
* The Octave Day itself is a Duplex feast and carries precedence in occurrence and concurrence accordingly. It is not transferable, however, when it occurs on a privileged Sunday, in which case it is to be commemorated in the Sunday's Office, e.g. Octave Day of the Immaculate Conception falls on Gaudete Sunday.
* The psalmody when the Office is of the Dies infra is ferial at Vespers and Mattins and festal from Lauds to None as is the case for Simplex feasts; all other texts are taken from the feast day itself or Proper as noted.
* The lessons at Mattins on the Dies infra are ordered such that the first two lessons and responds are taken from the occurring Scripture, lesson two being the concatenation of the second and third lessons from the occurring Scripture; the third lesson is formed from concatenating the pre-Sarto second nocturn lessons for the day in the Proper into one lesson (or using only the text which is Proper and not from the Common).
* During the entirety of these octaves, unless specifically stated to the contrary, any proper doxology and/or melody for the hymns for the particular octave is to be observed continuously. However, during the Octave of the Immaculate Conception, when the Office is of the Sunday or Feria, the Advent formulae are observed, but during the same octave when the Office is of a feast without a proper doxology, the formulae of the BVM are observed. The same rules hold for the verse at the short respond at Prime.
* Unless otherwise stated, the colour of the Office and the Preface at Mass are determined by the octave on all days within it, including Sundays, except in Advent or when higher privileged octaves hold the determining rule. The Credo, by rule, is omitted during Simplex octaves unless the Mass of a particular feast (or a higher concurrent octave) occurring within it requires it, e.g. Doctor of the Church.
This, we believe, is the best approach to borrow from Sarto's organization and distinction of octaves without sacrificing the nature of octaves (i.e. there are still days within). This also accords further usage of the ferial psalms in our quest to achieve optimal and actual, and not just theoretical, usage of the Ancient Roman Psalter.
As a review, the remaining Octaves not listed above retain the usual Semiduplex rank and rite on the Dies infra and a Duplex Majus for the Octave Day. Furthermore, the Octaves of Epiphany, Pascha, Pentecost, and Corpus Christi are privileged to the exclusion of all or nearly all occurring feasts.