Continuity mistake: Gene Hackman returns a second cookie to Harrison Ford's dish that he hadn't taken - or perhaps it's the same cookie he picked up and returned a moment earlier. Either way, the cookie had suddenly appeared in Hackman's hands going from one shot to another. (00:30:35)
Other mistake: In the dream sequence, Harry knocks on the door of the hotel room that is mentioned in the conversation. When he later goes to the hotel in real life, we see the hotel room doors and the numbers on the doors, and the doors are exactly as they were in Harry's dream. Unless he was familiar with the hotel, how would he know these details in his dream?
Answer: The Movie has a soundtrack, and that lovely piano solo music is actually the theme song, composed by composer David Shire. You can find it here, on Amazon - http://www.amazon.com/Conversation-David-Shire/dp/B000N4P5XA/ref=pd_bbs_sr_1?ie=UTF8&s=music&qid=1202051411&sr=1-1.