In episode 1 Miss Elizabeth Bennett sits at a piano as she sings a simple song while the score on the piano shows the name of (Johannes) Brahms, who was born sixteen years after Jane Austen's death.
A musician in the assembly hall dance scene is playing a concertina. The concertina was not invented until the 1820's, and the story begins in the autumn of 1811.
At the very beginning when she plays the piano, her right hand doesn't match the melody. The melody progresses towards the treble and her right hand goes towards the left side of the piano, i.e. the bass.