I know the notation for this exists, I am just not sure where to find it. The text for the antiphon is the following:
"Stans in Oratorio dilectus Domini Benedictus, Corpore et Sanguine dominico munitus, inter discipulorum manus imbecillia membra sustentans, erectis in cælum manibus, inter verba orationis spiritum efflavit; qui per viam stratam palliis et innumeris coruscam lampadibus, cælum ascendere visus est."
How’s your ear training? It’s not the notation, but if you have relatively decent ear training, you can transcribe it from this recording. It’s in organum, but both lines are very decipherable. https://youtu.be/Ka3MlU3tJ_o?si=g9RjiXzClWRx45Y7
The antiphon is nowhere to be seen before the 19th c., appears in devotional (not liturgical) books, mostly linked to the Solesmes abbey. Likely introduced by dom Guéranger or some of his monks. If there is any music (older than the Kwasniewskian setting), it will be in some collection of various extra-liturgical chants. I had no luck searching.
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