If you want to get some idea of what samples they used in final fantasy seven, load up the PC version of final fantasy 7's soundfont.
They appear to not only have used a sound canvas soundmap, but many additional vintage analog synth samples. (synth strings, Prophet, etc)
Some of the more intersting samples.
016 Hammond Organ. They usually don't call thsi sample "Hammon Organ" outright...
017 - B3. this appears to be a Hammond Organ set on percussive with a large amout of grit and character to it. This sample is what makes Still More Fighting what it is. The XG version pales by comparison, substituting a standard rotary rock organ.
081 bank 2: Moog2 (gee wonder what this is.)
80 bank 1: Prophet
79 Vank 2:Prophet Ocarina
54 bank0 Gstr: Voice
51 bank 0 Laments (nromally strings in gm?)
FInal Fantasy games use their own software wavetable midi synth on psx pr ps2, and internally the file are often MIDIS, which then get ripped out and connverted to GM/XG/etc.. The ps1 and 2 sound chips have hardware reverb/chorus in themi belieeve as well which cleans up the sound.