These songs really need no introduction, but for the sake of reviewing, I'll introduce them. Kyrie Elesion is a straightforward (by Fates Warning standards), fast speed metal song. Epitaph is a much more convoluted (and this is convoluted even by Fates Warning standards!) uber-epic that goes through numerous changes. Non-extreme metal has rarely been this dark. They are played in pretty much the same manner as in The Spectre Within, though there are some minor differences, such as the lack of keyboards in the last minute of Epitaph.
The main difference between the demo version of the songs and the full-length of version of them is, of course, the production. At first glance, the production does not seem to be very different from that of the full-length. But this demo is very bass-heavy, and the treble is obscured. The bass guitar is unusually loud, but the vocals and the leads sound like they are filtered through some barrier that takes away their power. This is quite a problem because John Arch's vocals (and his complex vocal lines) are the core of this band. The songs are still very much enjoyable, but there is really no reason to listen to this demo when you can listen to the album version of the songs. Except for one thing.
There is something hidden: when Epitaph ends, there is about a minute of silence, and a voice appears. It says, "What I want you to see is, these album jackets are not just thrown together -- there is a message that they intend to preach to you, in these religious albums. I say 'religious albums' because you can serve the Devil or you can serve the Lord. And these are not albums that serve the Lord -- they are albums that serve the Devil and are religious in nature."