yea there are some songs that you can play backwards.
Love Like Winter, Miss Murder, Prelude 12/21, He Who Laughs Last..., Girls Not Grey.
then on I Heard A Voice the little "hidden" clips that Davey, Hunter, Adam, and Jade have could possibly be another clue. this might not help much but its just some other little hidden things that might lead you to other thoughts on figuring the mystery out.
(my major focus is on Sing The Sorrow and Decemberunderground though...)