Deliverance (1972)

IMDb claims this film had a 70 mm 6-track mix. I've no idea whether or not the 5.1 track on the blu-ray is this same mix.

In any event, it sounds pretty bad -- very muffled and lacking detail. The Dolby surround track on the 1992 Warner LaserDisc sounds clearer (less NR) but is otherwise similar - the same murky, strange mix.

But the even older 1984 Warner LaserDisc sounds wonderful. It possesses a very different, much more aggressive mono mix. Ambient sound effects like footsteps and insect noises are much more prominent and lifelike.