Good ol Drop D
It never fails!
Anyhow, this is pretty sophisticated song. The Intro surprised me alot because this song is very different for what ive used to hear from you, in a good way. There is alot going on that in the end clash into one big chorus(??) and your guitar work is pretty sweet. Some parts I think were a bit off but thats a question of taste. Musically this is very good, great playing, great mixing, great quality.
Keep It up and stay metal!