Possibly... In the actual GD-ROM data of Sonic Adventure, there are 3 songs never used in the game, only one of them heard in the Tokyo Sonic Team Conference of August 22, 1998.
Anthaemia. said:
There's no doubting the importance of this disc to Saturn enthusiasts, but what's being lost is the fact that Sonic X-Treme in any playable form will never live up to the expectation and hype surrounding this title, or at least that's the conclusion I had to come up with based on everything I've read about the game so far. I definitely consider myself a massive Saturn fanatic, though I'm still not really sure why so much fuss is being made over this particular game when there are more complete prototypes (and some finished masters) in existence that are going to waste - surely it would make a lot more sense if the community worked together in order to save these as opposed to what is a glorified demo disc? If the E3 build or even a later PC version was leaked, we might even be able to get more from the X-Treme myth. As it is, most people seem content to just have what's available instead of looking for anything else. Then again, is the new owner of X-Treme actually releasing anything? To pass the time until we get some kind of answer to this question, somebody could get in touch with the former STI members who are known to have their own builds, as these may have more content. Also, as I said before, there are other games out there which are of interest, and many of these are more complete than X-Treme ever will be. Unlike this game, however, I have a feeling that obtaining something like Virtua Fighter 3 would require a lot more effort, so why isn't more of an effort being made searching for the many unreleased Saturn titles that are currently (and presumably) locked away somewhere?
P.S. Although both games were developed by two completely separate entities within Sega, there are some uncanny similarities between Sonic Adventure and (what has been seen of) X-Treme. However, to say that one is a port of the other would be completely wrong. The most realistic assumption is that Sonic Team was looking over its proverbial shoulder, taking what it considered STI's best leftover ideas for its own Adventure. Certain musical themes in this game were also used in the MegaDrive version of Sonic 3D, and if you also think of Sonic World on the Saturn as an early prototype of how the character would function in a polygonal environment then it's possible to create quite a lengthy timeline for Adventure's gestation period. Once again, though, I must emphasise that X-Treme did not become Adventure. In fact, Yuji Naka probably didn't want STI to use his team's NiGHTS engine because it was also powering an early Saturn attempt at a 3D Sonic game - could the hidden bonus in Christmas NiGHTS be another clue as to the true origin of Sonic Adventure?
One is named Sonic_CD.adx, and the other 2 are Nights_A.adx & Nights_B.adx. The files large, so I uploaded them with an ADX player to the rare media FTP.