Full film here for when you have a couple of spare hours.Indeed. So much so that I can remember little else of the film, not having watched it in many years, but that particular scene has stayed with me. Probably the best anti-war moment of any film, and I include 'All Quiet.......' and 'Paths of Glory' in that.
As you say, the sheer starkness, the reaction - or lack of - from the troops and the most inappropriate music elevate the shot to what I would consider greatness. A scene that in any poll of best scenes ( whatever the term) would rank with Welles in 'Citizen Kane' and in 'The Third Man'