Continuity mistake: When Mitch is trying to find the hand, Glen grabs the map. When he grabs the map there is a hole in it, but before he sets it on fire, the hole is gone.
Continuity mistake: When the chuckwagon is going over the cliff, keep your eye on the orange water barrel. First the lid on it flies off, then at a different angle, it still on, then once more at a different shot, it is off again.
Audio problem: When Mitch says to Duke "Oh, Curly, I am so sorry for burying you", his mouth is not moving.
Continuity mistake: When Mitch goes into work he is watching one of the radio psychologists at his station live on-air. The clock in the background clearly reads 1:30, nice that he's able to start work in the afternoon one thinks, but later he addresses the company meeting "Good morning everyone".
Answer: "The Godfather Waltz", the main title theme to the Godfather film. It's a reference from early where Glen is a fan of the film.
Bishop73