If you don't know this piece, well its ok...it isn't widely known although it should be. It is a movement from "Church Windows", by Respighi. It is pretty fine stuff.
You probably won't go away humming it either. Just take a minute sometime today and relax to it.
Matins is part of the church day and said at night..best rwo hours after midnight..lauds at sunrise, matins in the hours before; think pre-dawn song of the birds...that's what I remember anyway and being Lutheran, well, I/we observed Matins at times, as it was a respite of reflection and a time to prepare ...anyway.
Just enjoy it and put yourself at peace.