This Integral OST, is the complete Digital Devil Saga OST out there. All of the songs from both games are composed by the great, Shoji Meguro, with an exception to Alive (DDS2 Opening Song).
Most of the songs are well-balanced mix of rock and pop. These songs definitely fit the setting of the games with motivating themes.
This is a soundtrack of excellence that you shouldn't miss. So I'll give it a 10 out of 10.