This is the one thing that makes me worry my theory is incorrect, and that perhaps an alternate timeline explains it better.
Perhaps there’s a way to reconcile both ideas? I mean, if we were to assume that Aerith or Sephiroth at least possess some level of foreknowledge, then I think in a sense they are reliving certain events.
I don’t know if it’s a matter of Aerith or Sephiroth traveling back in time or if they just have knowledge of the future that they’ve yet to experience, but if I’m not mistaken, it’s at least confirmed that the remnants of Sephiroth from AC actually have traveled back in time via the three Whispers that form Bahamut during the last chapter.
I guess Cloud’s visions might also have something to do with Jenova/Sephiroth messing with time but it’s anyone’s guess at this point!
Hmm, I can't seem to find it in that scene... also, the OST PLUS tracklist has a track titled "Elmyra's Reservations" which is separate from "Aerith's Theme - Memories".
The melody of Aerith’s theme can really be divided into three phrases, with the beginning of the first phrase being the most recognizable probably because it’s the beginning of the song and also it’s association with the OG cutscene of Aerith’s death as the white materia falls into the water of the Forgotten City.
From 0:50 to 1:33, the music is like a slower version of the third of these phrases in Aerith’s theme (can I just say, that subtle shot of Barret when Elmyra says Aerith’s not her daughter by blood is friggin’ brilliant).
Throughout the cutscene, the music mixes original stuff with bits of Aerith’s theme save for specific moments like 2:32 where it directly uses the first phrase of Aerith’s theme, or the use of the second phrase at 3:52 and the third phrase at 4:25.
Once Tseng arrives at 4:58, the music switches to a more ominous theme that itself is also a take on the melody of Aerith’s theme mixed with the melody of the infiltrating Shinra music (I absolutely adore when the remake does stuff like this with the music).
I think “Elmyra’s Reservations” is the music from the later cutscene after Cloud and the gang bring Wedge to Aerith’s house and Cloud requests Elmyra’s permission to save Aerith for the second time, right before the chapter 14 resolution.
