Snoke Theme and the Opera House theme
Wow, I am really shocked there is a connection between Ep 3 and The Force Awakens. I've heard a lot of theroies about the origines of Snoke, the main bad guy leader. However, a lot of people think he's Darth Plaqueis in hiding. The score is very similar to the Snoke theme in Force Awakens.
Here's the track comparison. It is very uncanny how similar they are.
Keep in mind that SW does this all the time. Ankin's theme has Vader's theme hidden in it.
And, Palpatine strongly implies that he betrayed Plagueis himself. Palpatine probably thought he killed Plagueis and then moved on to build his Empire. Plagueis brought himself back to life and went into hiding. When the Empire fell, Plagueis changed his name and rebuilt the Empire into the more militant First Order.
Plus, it looks like Snoke has been disfigured by a weapon of sort.
I kind of hope they go in that direction.
Side Note: Palpatine also looks at Skywalker when he says, “create life” thus implying that he or Plagueis created Skywalker.
Now, there is another theory...
Side Note II: I did an image search for Snoke Google suggested “Snooki Weight Loss”. Thank you, Google. Maybe there is a connection between Snooki and Snoke. They're both evil and command a bunch of crazy people. (yes, I went there. I kid.)