The Gorillaz - Plastic Beach has an opening track appropriately named 'Orchestral Intro'.
Pop albums with an opening overture?
Ray Thomas album "From Mighty Oaks" has a very nicely done opening orchestral overture of the album by the same name. Never thought about it before before digging this album out for conversion to music library. Not a very common thing for a non themed pop album to do that. Any others come to mind?