"One-Winged Angel" is the musical theme for the final boss of Final Fantasy VII for PlayStation, released 1997. I no longer have my copy, sadly.
In spite of consisting of no less than three CDs, the game's soundtrack, either mostly or exclusively (that's the question), uses not CD audio tracks for the music (besides the FMV sequences), but rather the PlayStation's built-in "MIDI"-like sound chip/mechanism. That is, it stores an efficient and compact series of signals for which instruments to play and when, rather than an actual "audio stream" like a CD audio track.
However, the "One-Winged Angel" song sounds quite a bit different from the other melodies in the game. And I'm not just talking about the fact that it has vocals. It seems to be using a traditional orchestra, which I wonder if they really had virtual "instruments" for inside the PlayStation.
I suppose it's possible that the PlayStation audio format does have the required instruments, and then they added the few repeated audio samples on top of that in the game engine, while playing the melody, but it sounds to me as if they made an actual CD audio recording of the song and used that in the game for this particular song.
Can somebody please verify or reject my theory? I've tried to find out on my own.
This is the song I'm talking about: https://www.youtube.com/watch?v=qDD-iYkHBhc
PS: I'm only talking about the original game -- not the butchered re-releases.