The award for the most effective piece of classical music in a film goes to......

[chomalungma]

Well - lots of candidates.

But I think that Variations on a theme by Thomas Tallis ...by Vaughan Wiliams which is used at the end of Master and Commander just after the battle when they are reflecting on their losses has to be a contender.

Plus the use of the Enigma variations in Dunkirk when the little ships arrive.

A perfect use of classical music to fit a scene in a film.

So what's yours?

@PerkingFaintly, thanks for that. I'm always in tears at that scene, but that adds a whole new dimension.

Another vote for Apocalypse Now.

I was absolutely sobbing in Dunkirk when the Enigma Variations came on. It's one of those pieces that makes me cry, but also makes me hate myself for crying at it.

Tempted to add John Williams's use of Mahler in Star Wars

Ooooh, and Kubrick is an absolutely master of sound. I love the way he uses music to comment on the action, creating a critical gap between the visual and the aural. Basically, the soundtrack to Barry Lyndon is a masterpiece.