The Harry Potter series has had a whole load of different composers, but Alexandre Desplat took over the reins soundtrack-wise in Part 1 and is here to finish out the series in the big finale.
As we've mentioned in previous learning guides, the music for the Harry Potter movies has been pretty consistent, despite lots of switch-ups in composers, and this film is no exception.
The music definitely does a lot to underscore (pardon the pun) what's happening, with loud, thunderous music droning on during action sequences and spooky strings if suspense is building. Also, there are what we like to call "sad strings," which crop up particularly when there's been a lot of death and carnage (which the Battle of Hogwarts produces in droves).
All in all, it's a soundtrack worthy of all the drama, action, suspense, tears, and triumph that mark the end of the series.