I read through the booklet lyrics on first listen (annoying as it was given the packaging), which was enough to get the story in one go (apart from a couple of things only described on their site such as Daryus's deafness, exactly what "Bug" is...). Normally the vocals in combination with listening to the lyrics and having a basic understanding of who the characters are is enough to tell who is meant to be speaking, but in some cases the lyric booklet is probably necessary to tell, and there is virtually no way to tell just from the vocals alone, and you need to go by the lyrics. For example, in what I would call the second and third "chorus" of A New Beginning (although the lyrics are different each time), there is little if any difference in the vocals to distinguish between Faythe and Arabelle and then Faythe and Nafaryus. But for most extended sections from one character, it does a good job of making it feel different.