Now the term "mono" will elicit a variety of reactions from people; some will be overjoyed, some won't care, as mentioned above, some will ask "what's mono?" and Wayne Campbell will say it's what he thought he had once, only to find out he was just really bored. Let's go with "what's mono?" first. In reference to a film's soundtrack, Mono (or monaural) means a single signal being sent to speakers, so while many tracks can be recorded (music, dialogue, effects etc), it will all be mixed down to one signal for the final soundtrack and included on the film print itself.
This may sound an odd thing to do to your average 21st century moviegoer, who is used to going to the cinema and getting a THX-certified DTS track coming out of your forty-six speakers and twenty subwoofers, but once upon a time in the movies that was the standard for most pictures. Many cinemas just didn't have the money to install the expensive equipment needed to reproduce stereo sound, so most of the pictures of the time were exhibited with a mono soundtrack, at least until Dolby Stereo hit in 1975 and made it widespread. So onto the next question: why are people overjoyed?
Firstly, because the original soundtrack is being presented. This mean it's how the film was originally seen and as a result is an important document in the historical sense, providing an interesting comparison between original theatrical presentation of the days gone by versus today's cinema patrons, of which even the most casual generally have at least a basic surround sound system in their home.
Secondly, because it's the way we remember it. Obviously, remixing a monaural or stereophonic track into 5/6/7.1 surround is a tricky business, so to get the right discrete effect with the surround track (i.e the placement of the effects that make it really feel like the sound is all around us) there are two options: either go back and remix with the original sound elements or create new elements using foley. With the Jaws blu-ray soundtrack - which I've reliably been informed is an upmix of the 5.1 track found on the previous two DVD releases - they went for the second option.
Now, I don't want to be presumptious on Universal's part in terms of why they decided to go with recording new elements; it could be that the original elements weren't available to them separately, which is understandable. But as a lifelong fan of the film it was disappointing to buy the original DVD on its release date in 2000 only to find some of the iconic sounds from my years of movie-watching replaced (I wasn't alone, the Internet Justice League of Movie Nerds blew up over it). This is probably going to sound really anal to some, but it's like buying a new remastered version of Let It Bleed and throwing on 'Gimme Shelter' only to find they've inserted a new vocalist singing Merry Clayton's lines.
This didn't just happen on Jaws. The DVD release of James Cameron's 1984 classic The Terminator featured a remix with some ugly rerecorded sounds, mostly from the cavalcade of guns being fired throughout. Similarly, the various special edition reissues of the Star Wars Trilogy have had their fair share of replaced sounds, from the addition/deletion/replacement of dialogue (for example, when Darth Vader prepares to depart Cloud City in The Empire Strikes Back, his original succinct (and angry) line 'Bring my shuttle.' was replaced with a outtake from the original Star Wars, 'Alert my Star Destroyer to prepare for my arrival.' Most recently, in the blu-ray edition of Return of the Jedi, John Williams' brilliant cue for Vader's redemptive moment was ruined by the infamous insertion of a scream of 'Nooooo!'
Talking of redemption, Universal did themselves a favour when they reissued Jaws on DVD in 2005. Not only did they include the full two-hour 'The Making of Jaws' documentary from the original Signature Collection laserdisc, they included the original mono soundtrack. And it's beautiful. Thankfully, this will also be on the upcoming blu-ray, so not only can you experience the film as it was meant to be seen, you can still experience it as it was meant to be heard, with its original Oscar-winning soundtrack, warts and all.
So this is a call to studios everywhere, by all means continue remixing your soundtracks for whatever new-fangled audio hardware is available to the consumer, but please remember to include the soundtrack as it was originally intended, whether it be mono, stereo or hyperphonic 9.6 Dolby XXX. Entertainment is a top priority, but preservation is just as important.