Hasn't it been confirmed that Styx had Lou DePasqua, offstage, adding extra vocals, during the 1996 reunion tour? Is is safe to assume that he stuck with them for the 1997 tour.
I recently saw a video of them playing Queen Of Spades, in 1997. While I am certainly NOT suspecting any trickery, I noticed that the big, high note after the solo sounds like it might be another voice. Perhaps Lou handled it, off stage, to help Dennis?
https://youtu.be/3-jEeHcci0s?t=4m30s
I feel like the tone of that note seems a little to "shrill" to be Dennis's voice.
(Once again, I'm NOT suspecting lip syncing or anything.)