I don't know where to find the score, but if your friend can play by ear, here's a youtube
of a choir singing it. They spell it "Angelsko cescenje" and translate the title as "Angelic adoration."

https://www.youtube.com/watch?v=e5mzW46wyuw

The choir is from the now-closed Holy Trinity Catholic Church in Indianapolis, which has been merged with another parish. There's also a Slovenian choir in Ely, MInnesota.

Hope this helps.

"Angelsko češčenje" is a term used for the Angelus prayer (The custom of reciting it in the morning apparently grew from the monastic custom of saying three Hail Marys while a bell rang at Prime. The noon time custom apparently arose from the noon time commemoration of the Passion on Fridays. The institution of the Angelus is by some ascribed to Pope Urban II, by some to Pope John XXII in the year 1317. The triple recitation is ascribed to Louis XI of France, who in 1472 ordered it to be recited three times daily. The form of the prayer was standardised by the 17th century.).

The prayer in Slovenian:

Angel Gospodov je oznanil Mariji – in spočela je od Svetega Duha. Zdrava, Marija …
Glej, dekla sem Gospodova – zgodi se mi po tvoji besedi. Zdrava, Marija …
In Beseda je meso postala – in med nami prebivala. Zdrava, Marija …
Prosi za nas, sveta Božja Porodnica. – Da postanemo vredni obljub Kristusovih.
Molimo. Nebeški Oče, po angelu si nam oznanil učlovečenje svojega Sina. Posvečuj in podpiraj nas s svojo milostjo in nas po njegovem trpljenju in križu pripelji k slavi vstajenja. Po Kristusu, našem Gospodu. Amen.