^

Even on Advent Children?

Uematsu has used Shiro Hamaguchi most of the time for orchestrations. Sekito, however, hasn't used any orchestrator for his works. Kenji Ito orchestrates his own stuff.

Uematsu didn't do any arrangements (orchestrated or otherwise) for the soundtrack. They're all done by Shiro Hamaguchi, Kenichiro Fukui, Tsuyoshi Sekito etc. Uematsu just wrote (most of) the music. I kind of wonder how much of a hand Uematsu has in new arrangements of his old tunes, that is to say, whether he just lets others go wild with his original compositions, or first re-composes (arranges) this own music so others can use it as a basis for their arrangements. My guess is it's mostly the former option, with Uematsu overseeing the arrangements as they're being created.

Edit: I lied; Uematsu did actually arrange track 8 (Water) on first disc of the soundtrack, along with Keiji Kawamori), though it's a newly written and non-orchestral track. Sounds like something from his Phantasmagoria album.