I think some people involved with the album have heavily alluded to the reasons...
I have no inside knowledge myself, but it seems that we're talking about two composers who are still alive and kicking. I wouldn't think that either would really want to share the album space with the other.
And of course, there's an embarrassment issue involved as well. Would Silvestri want a score that he was only able to record for a few days (and which was unceremoniously tossed) out there? He didn't have time to finish or refine it, really. And would he sit for an interview to talk about it? I wouldn't think he'd want to.
It would sound like Hollywood poison for anyone involved to go down this road. Especially since a number of the filmmakers involved (and Tom Cruise himself) are still very active in the industry and the Mission Impossible franchise is still going. I don't think any of these people would sign off on "Hey, remember that guy we fired 23 years ago?" release. It took them six f'ing years to sign off on an expanded release of the score they DID use in the final movie!
Thanks John! There's actually some good points here. That was the kind of statement I was looking for. The embarrassment issue looks pretty much legit. Even if in my humble opinion Silvestri score was anyway amazing, I like very much the Elfman replacement one but still have a preference for the unused.
Thanks for the info about the alternate tracks, I’m really looking forward to getting this.
Any insight into the process of changes for the score is fascinating because Silvestri and Elfman’s scores work so differently. It’s interesting to note the stylistic differences and how they resonate in the film. Since Elfman had such a short time too, the evolution (if any) of his work is also really insightful, especially for an action cue like the train chase because that sequence in particular is so strongly driven by the beats throughout it that I’d imagine it was one of the tougher cues to work out.
It’s also interesting that both Elfman and Silvestri started that sequence with music, but the music editor chose to fade up the music much later in the sequence and let it establish itself solely through the SFX/foley tracks.
It also seems like in general there were a lot of music editing tweaks to crossfade and loop certain sections in the movie.