I presume you are using the Little Office of the BVM...

Here is a full version with music...

https://www.dropbox.com/s/5jet8rmoy2cdlrz/Little Office B.V.M..pdf?dl=0

Anyone who wants to, PM me and I can email you my work-in-progress book for singing the Little Office, for your personal use and non-distribution. One of these years I will finish it...

My theory for a long time has been that since the AR is silent about this issue, the least inventive solution is to just use the common tones in the same fashion as for the full office.

A thing I have wondered about: how exactly did the AR foresee its music for the Little Office being used? Was the Little Office seen as a stand-alone service, or something to be inserted into the singing of the full office? Or was the music just included "lest it should perish"?

The 1893 Le Petit Office is a self-contained book, published by Solesmes. If you want to discuss common tones within that context, that is as far as it goes. Anything not included in the book was not part of that particular self-contained scheme for singing the Little Office.

The 1890's were a great heyday of publications by Solesmes. In their initial vigor, Solesmes covered a huge amount of ground. When after the turn of the century Pius X's committee began to bring forth their typical editions, the "Vatican Edition" Kyriale, Graduale, Antiphonale, etc. in general superseded the previous editions by Solesmes which covered the same material.

For better or for worse, the Vatican Edition ended up not covering quite as much ground as the earlier editions of Solesmes. This is the reason why in the Liber Usualis you will sometimes see certain chants annotated as being "from the publications of Solesmes". Using the earlier editions from the 1890's was seen as the best way to fill the gaps in the authoritative-but-not-yet-comprehensive Vatican Edition.

Matins for Pentecost and Corpus Christi are two examples of this. What the Liber does is take the Invitatory/Antiphons/Responsories from, say, the 1895 Liber Responsorialis; but then it gives the melodies of the Hymn, the common tones, and the Te Deum all according to the Vatican Edition.

This same method can be followed for Matins the Little Office. Matins is the main problem with using the Vatican Edition for the Little Office, since the Invitatory/Antiphons/Responsories for the Little Office for the most part do not exist in the Vatican Edition.

You would then be left to make heads or tails of how the common tones of the Antiphonale Romanum should be applied to the Little Office. As I stated above, the conclusion that I have reached in long thinking about this is that the least inventive solution is to just use the common tones found in AR in the same fashion as they are prescribed for the full office. Once you make that decision, there is not much of a problem in figuring out the rest.

I really think that one should use the Vatican Edition as much as possible for singing the Little Office, because otherwise the chant for the Little Office is not anchored in its correspondence to the same chants as used in the full Roman secular office.

Yes, it basically follows the Vatican Edition and supplies the chants for Matins from Holger Peter Sandhofe's Nocturnale Romanum.

Note: it is not set up as a singer's book.

The 1893 edition of the OPBMV is extremely helpful! I was searching high and low for some of these chants for my own praying of the Office and this just pops up.