Continuity mistake: As Hubert says, "They put the French army in an impossible situation where they couldn't win." Notice Roxanne and the people next to her, whom are bathed in sunlight, in the next shot the woman has no sunlight on her at all. (02:09:30)
Continuity mistake: Close to arriving to the French plantage, and also when leaving it, Captain Willards' helmet cover changes between a plain olive green and a camouflage.
Continuity mistake: After the 'Valkyrie' helicopter attack, there's a close shot of a soldier who shouts: 'I'm not going.' Another soldier turns back to the chopper to pull him out. Then there is a long shot of the troops at the choppers and you see the same soldier turning back to the helicopter. (00:42:15)
Answer: It's not any specific song; it's just the kind of generic piano music you'd hear at dinner at a high-class restaurant of the era. Think of scenes in movies, films, etc. set or made in the '50s and '60s, where the characters go to a nice dinner and there's someone at the piano playing unobtrusive music to accompany the food/conversation.