Continuity mistake: As they start to eat with General Corman there's a hat hanging on a cabinet behind and to the right of the general and both doors are closed behind it. The next time we see it the right door of the cabinet has been opened but no one went near it. (00:11:45)
Continuity mistake: No one has touched it, but when the General passes the roast beef to Jerry, the pepper shaker, which was just next to the salt shaker in front of him, has been moved to the other side of the table. (00:12:00)
Continuity mistake: As Jerry takes a piece of roast beef from the tray we get a close-up of the captain's table setting. Just about everything has been moved from the previous shot but his bread dish and napkin are the most notable as they have both moved to the right of where they were before. (00:12:10)
Continuity mistake: At dinner with the general, Harrison Ford walks over to the captain with the picture of Colonel Kurtz and he has a pencil in his right hand. In the next shot as he drops the folder on the floor the pencil is not there. (00:12:25)
Continuity mistake: As Harrison Ford hands the Captain a picture of Colonel Kurtz note the salt shaker and spoons to the right of his plate change. The salt shaker disappears and the spoons are suddenly side-by-side when the Captain places the photo on the table. (00:12:30)
Continuity mistake: At the dinner table General Corman tells Harrison Ford to, "Play that tape for the captain please" and we see a close-up of his watch and it reads 4:37. It's late for lunch but when Harrison Ford brought the can of Budweiser to the general it was lunchtime as his watch read 12:35. (00:12:35)
Continuity mistake: Harrison Ford goes over to the tape recorder to play a tape of Colonel Kurtz' voice and the food on the captain's plate changes completely. At first there's a serving of roast beef with a roll next to it, than when we see it again there's less roast beef and pees and carrots where the roll was. (00:12:55)
Continuity mistake: When Colonel Kurtz says, "And they call me an assassin," the statue in front of the TV casts its shadow on the left of the picture tube. The lighting doesn't change throughout this scene but the next time we see it the shadow is one quarter of the way to the center of the picture tube. Later the shadow moves back to the side of the TV again. (00:13:55)
Continuity mistake: In the close-up of the General when he says, "He joined the special forces.", note his collar is closed up more and they way the front of his hair is combed changes between shots. (00:14:40)
Continuity mistake: As the general reminisces about Colonel Kurtz being a man of, "wit and humor" the roll on his plate moves and changes from being whole to having a bite out of it and back. (00:14:40)
Continuity mistake: After the General says, "And very obviously he has reached his" there's a close-up of Captain Willard and his face is dry. The next time we see him a few seconds later his face especially around his chin is sweaty. (00:17:10)
Continuity mistake: Captain Willard thinks to himself about how many men he may have killed in the war and we see the PBR up close for the first time. The crew on this boat is not the same as the crew we'll be meeting shortly because at least four of them are white. (00:19:25)
Continuity mistake: When Captain Willard flies in by helicopter to meet up with the PBR at the Texaco fuel depot, we see only one PBR with a flag waving in the front and a radar dome on the back of the roof. This is not the same boat that we see in the next shot in which the flag and radar dome are reversed. (00:19:25)
Continuity mistake: There's no indication that Captain Willard didn't leave for his mission immediately after having dinner with the General, being that his R&R was over. That nasty cut on his thumb is all healed without any band-aid on it by the time we see him in the next scene on the PBR. There was also a dark scab on his middle finger that was there as he smoked a cigarette in the end of the scene with the general that has also disappeared. (00:20:30)
Continuity mistake: Near the beginning of the movie when we first see Chef's tattoos up close the tip of the serpent's tongue on his left arm is entirely red. Later in the movie before he gets onto the Vietnamese sampan we see it again up close and the tip of the serpent's tongue is green. (00:24:05 - 01:35:55)
Continuity mistake: After Captain Willard looks at the picture of Colonel Kurtz being decorated by General Westmorland, they're all startled by the "Arc light" B-52 strike, note the rear machine gun is pointing forward and a helmet is hanging from the middle machine gun. In the next shot the rear machine gun is pointing aft and the helmet is now gone. (00:24:05)
Continuity mistake: Clean's dog tag and cross change between scenes. When he first hears the "Arc light" B-52 strike we see the cross hanging at the same level as the dog tag then when he meets Colonel Kilgore the chains have been rearranged so that the dog tag is two inches lower than the top of the cross. (00:24:10 - 00:30:05)
Continuity mistake: Captain Willard is wearing green, tan and black camouflage trousers on the PBR when they spot Kilgore's air-cav unit. They immediately proceed toward shore and as he jumps off of the boat he's wearing different camouflage trousers, which are brown and green. (00:24:15 - 00:25:15)
Continuity mistake: As they all sit on the boat and listen to the "Arc light" B-52 strike Lance is sunbathing in direct sunlight. In the next shot he's in the shadow of the roof of the boat as he gets up and says "there they are". (00:24:15)
Continuity mistake: On the boat as they look for the B-52's, Lance says, "There they are," standing in the center of boat under the flag. In the next shot, Clean is standing in that spot. (00:24:25)
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.