The classical music playing in the background at the start of the funeral scene at the red church is Canon in D Major by Johann Pachelbel. The joke being that, Canon in D Major is actually a wedding piece, not a funeral piece.
Pachelbel's Canon in D, heard at the funeral, was in obscurity for centuries but regained popularity by the 1970s. Since then, elements of the piece, especially its chord progression, were used in a variety of pop songs. It has also found increasingly common use in both weddings and funeral ceremonies.