Sherlock and his violin
Regarding the soundtrack for S4, I've noticed a new motif that originated in TST, a sombre violin piece that begins at 1:13 on track 6 'Running Away', used for the scene where John reads the letter Mary wrote about running away. So naturally I assumed this was Mary's theme, until today when I heard it again in TLD (track 7 of the TLD soundtrack 'No Charges' at 0:45), but slowed down. The scene in TLD is where John hits Sherlock, so it has nothing to do with Mary. What may we deduce of this?