No interactions present.
I do not remember the sound it made
The ones I saw/heard displaying in Slovenia (identified by Michael) in the link above were very distinctive - with the males doing short display flights, then perching on rocks or plants to make a series of short churrs then long loud ones with the wings fanning, similar to some I've seen in the USA but never before in Europe. But maybe yours were just resting!
Nick Upton, naturalist and photographer.
Lat/Lng: 46.0588, 8.08827