Chapter 20 contains the Original Theatrical Trailer.
The digital/analog audio on this disc retains the "Sensourrond" low frequency information.
Additional Information by disclord
The Midway trailer included on this disc was made for theaters equipped with the Sensurround Special Effects System, and is presented on this disc in UNDECODED Mod-II Sensurround; this means it hasn't been decoded with a DBX Type II noise reduction decoder, which Mod-II Sensurround utilized to allow mono optical soundtracks to offer the fidelity of magnetic sound and create greatly increased dynamic range for the Sensurround effects - playback without DBX is why the trailer sounds so harsh and bright. Decoding the trailer's audio with a DBX Type II (consumer system) decoder will restore the proper sound dynamics and frequency response as well as reproduce the infrasonic low frequency Sensurround effects at their proper levels, giving a much better home recreation of Sensurround than the movie itself. This disc is the only format that contains a Sensurround encoded trailer, as the trailer included on the DVD of Midway is the non-Sensurround version and the low-frequency effects on the movie itself haven't been properly DBX decoded.