To turn the question: what's the good principle (*not* practical consideration) for treating the evening of 8/15 as OT 20 rather than Assumption? It's telling that such a principle is MIA.
Compline would still use the festal melodies, at least in the Liber Usualis (I have no idea what the new books would order) on Saturday the 15th...
Liam: the Mass as a part of the Office was an important theme in the discussion at the Colloquium with the Office choir.
And the feast day goes from the evening prior (at least on days of precept) to the midnight of the day following. So it is still the Mass of the Assumption in the evening... And a Sunday evening Mass is still Sunday, even after Vespers.
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