Re: Scary music
The first bass-y note of the electrical parade intro. Back when it was in Disneyland and Anaheim was slightly more desolate, you'd be sitting with mostly just some crowd noise and every time a plane would fly somewhere nearby it would make that jet engine sound very similar to the note and you'd think the parade was about to start.
Edit: Oh.. didn't read the "Scary" part only the "anxious" part. Well, I never went on Alien Encounters so that really can't count but I was petrified of ET and most alien movies and going through the forest, hearing the music, and having that sorcerer-ET pop up in the queue for the Universal ride had me shaking and terrified.