@Raizen1984
The reason why Dynamo and X vs. Zero can be specifically linked to Naoto Tanaka is because of the in-game credits for both games.
X5:
http://www.youtube.com/watch?v=XLe35S7nkY4#t=2m37s
Sound: Naoto Tanaka, Takuya Miyawaki with Shinya, Naoya Kamisaka
Sound Effect: Toshio Kajino, Atsuko Fujitani
X6:
http://www.youtube.com/watch?v=uFqfkBwlO-M#t=1m54s
Sound: Tosio Kajino, Jyunko Hujitani, Akemi Kimura, Naoto Tanaka
Since the OST only credits Kimura for X6, any chance the two poorly translated sound effect contributors had at contributing something music-related is zero. The X5 credits also indicate that Tanaka didn't do any sound effects; just music. Combine that with the fact that Tanaka and Kimura are the same person, and it basically breaks down to this:
"Akemi Kimura" = Naoto Tanaka's X6 work.
"Naoto Tanaka" = Naoto Tanaka's X5 work, which only applies to the two returning tracks from X5: Dynamo and X vs. Zero.
The way X6's credits are formatted are also generally the same as those in the two Mega Man Xtreme games. The text sounds (among many others) are the same between both of these games.
Xtreme 1 (
http://www.youtube.com/watch?v=hfcUSIGP4bg#t=5m37s) ---> Sound: Toshio Kajino, Saori Maeda
Xtreme 2 (
http://www.youtube.com/watch?v=BObjFoud8AM) [at 0:34] ---> Sound: Toshio, Mitsuhiko
Therefore, all of Xtreme 1's arrangements were done by Saori Maeda (aka Saori Utsumi) and all of Xtreme 2 was arranged by Mitsuhiko Takano
...
As for the difference in order in the X5 credits and the inclusion of Shinya Okada, it does not affect me too badly. Having Shinya's techno vibe in cooperation with Miyawaki increases the probability of the latter having done the two tracks I've associated with him, and another key point is the fact that NONE of the three have "(CAPCOM)" written next to them on Booklet Back. Whereas X5 was made back when Tanaka and Miyawaki worked for Capcom [The Kimura alias came with Naoto's move to Valuewave (X6-X8) along with Miyawaki (X7)], Kamisaka was ALWAYS outside of Capcom, so he was listed last in-game, but his position here still means that he was second-most in contribution to the OST after Tanaka. Therefore, since Tanaka had the guitar-representative rock style (i.e. Opening Stage Zero), Kamisaka must have the nearly-as-prominent synthesizer style (i.e. Opening Stage X).