I have begun a collaborative project with a Facebook friend of adapting the chant of the "praefatio in tono solemniori" found in the Missale Romanum (MR) to the English prefaces found in Divine Worship: The Missal (DW). My intent is to just adapt what corresponds to the prefaces in the MR. However, DW has many more prefaces than the MR, which makes me wonder what extra prefaces I should choose to adapt in order to "correspond" with the MR. For example, the preface of the Holy Trinity covers many Sundays in the MR, but only covers Trinity Sunday in DW. This causes me to ask a question such as "would this tone be used on a Sunday in Advent and so should I set the DW preface for Advent?".

Does the Missale Romanum "imagine" certain days these tones are to be used? Is there any rubrical guidance for them? Or other historical/traditional conventions? Or is it really just "ad libitum"?