Continuity mistake: When Mr. Collins introduces himself to Mr. Darcy, Mary is behind them, talking to her parents. However, you can hear Mary singing at the piano (in the next room) at the same time, and then go on to see her there in the next scene. (00:40:20)
Continuity mistake: Just before Mr Bingley proposes to Jane, when Mrs Bennet orders 'Everybody to the kitchen', Jane is holding her right hand over her left hand. When Mrs Bennet kisses her hands the next second, her left hand is over her right hand. (01:40:05)
Continuity mistake: During dinner at Lady Catherine de Bourgh's home, all five candles on the candelabra repeatedly grow taller or become shorter, depending on the angle of the shot.
Continuity mistake: Everyone is having dinner at Lady Catherine's house. Watch the candles in front of her. In the close-up shot of her face, every candle is standing up straight. In another shot, further away, the second candle from our left (Lady Catherine's right) leans towards the left side of the screen.
Continuity mistake: Kitty has just spotted Mr. Bingley returning to Longbourn from the window. She is seen through the glass wearing two bangles, spaced several inches apart, on her left lower arm. Cut to the immediate next shot from inside the room and the two bangles are now on top of each other on her wrist. (01:43:50)
Continuity mistake: The brown ribbon on Mrs. Bennet's bonnet during her conversation about the return of Mr. Bingley keeps moving back and forth over her left shoulder throughout the scene. (01:38:10)
Answer: The composer is called Dario Marinelli, the pianist is Jean-Yves Thibaudet. Marinelli composed the music that Lizzy and Georgiana play. The only thing he hasn't composed is the piece that Darcy and Lizzy dance to at the Netherfield Ball, which is a piece from Henry Purcell.