Underoath has gone through an impressive amount of change over the years, transitioning from deathcore into post-hardcore, losing Dallas and gaining Spencer, ultimately resulting in a variety of sounds. Lost in the Sound of Sepearation offers a considerable amount of change over Define the Great Line. Not only is there the customary difference in production, Spencer has completely altered the way he screams. His screams have become deeper, and more gutteral, resulting in a fresh sound the likes of which I haven't encountered before.
Track four, "Desolate Earth :: The End is Near", really puts Spencer's new style of screaming on display. While his new style of screaming can be refreshing, more often than not paired with Aaron Gilespie's clean vocals, there are instances where it can get to be a bit much, teetering on the threshold of bearability. "Desolate Earth" is one such instance. Spencer's held out, grinding screams really start to get under the skin not even halfway into the song. This is the one true problem that I have with the album.
While Lost in the Sound of Separation has its low points, as covered above, it has many high points as well. Songs such as "Breathing in a New Mentality", "A Fault Line, A Fault of Mine", "The Only Survivor Was Miraculously Unharmed", and "Desperate Times, Desperate Measures" really integrate Spencer's new style well. And as with your typical post-hardcore album, the heavy and the melodic are clearly represented. "Breathing in a New Mentality" represents the heavier side of the album, going full out and in your face, while "Too Bright to See, Too Loud to Hear" represents the polar opposite, consisting of nothing but melody and emotion. Underoath manages to flawlessly combine the heavy and punishing with the beautiful and melodic.
Lost in the Sound of Separation was handled by the same producers responsible for for Define the Great Line. The deliver impresive work the second time around, but when compared to Define the Great Line, something sounds a little off. Its difficult to describe, but Define seems richer and warmer to me, sounding overall a little more polished. Though worthy of note, that is by far not much of a problem.