Gravediggaz's 1994 track "1-800-Suicide" and At The Gates' 1995 track "Suicide Nation" have one word in common and maybe the fact that both bands have fairly morbid-centric imagery. Corretja has decided that both these songs fit together thematically and musically, and re-recorded them both as one super heavy melodic death metal track à la the mid-90s.
Sure, it's not a conventional mashup by the usual means of the word, but it definitely works and sounds pretty cool.
[via MetalSucks]