Continuity mistake: When walking along the cars at the start, John is level with the first car. Camera changes and now he is level with car 2. (00:06:45)
Continuity mistake: When the motorcycle hits Wick's car during the chase scene at the start, the motorcycle demolishes the front right quarter panel and door, with noticeable pieces hanging off the car. When Wick walks around the car to investigate the driver, the car appears to be in pristine condition. (00:02:05)
Revealing mistake: When John is escaping at the start, he throws a sharp left when a taxi appears ahead of him. Just before he takes the turn, we see a view from in the car. In this shot, you can see skid marks already ahead of him exactly where he's about to skid. (00:08:20)
Answer: String Quartet in A Major, Op. 55, No. 1, by Joseph Haydn.