Theory Help: Demonic Science (by Arch Enemy)

https://www.youtube.com/watch?v=Bw3hHX5nsdI
I was learning by ear and don't quite understand what's happening there (after 4:30).

The backing sounds easy enough. Em D C (all+4th) then B. Harmonic Em. Right?

Melody part(very short) sounds like:
Em leads to A, and D is not augmented
D G, which has C#
C#m F#, there we have A#

So is it common to have harmonic backing, while solo with natural 7th and augmented 6th, and a blues Bb (Eminor)?
Or is the melody part actually in Bm, then Bm harmonic?
I tried to play C instead of C# which sounds plain wrong and that made me prefer the latter. Does this thought make sense?

I never have anyone teaching me except my first a few lessons, so these may be nooby questions
Please feel free to tell me anything you think that can be helpful!

Thanks.

Need A Tip About Breaking Benjamin Style

This piece is pretty easy but sounds Fabulous so I want to dig into it to learn some music logic (I love to call it logic because it's science ) so in the very first part of arpeggio ,

Bb add9 (Bb D F C) without the Bb – 2nd voicing of Bbmaj add9
C major (C E G C) without the low C – 2nd voicing of C major
F sus 2 (F G C) using the root, 2nd and fifth

Why is it treated as Bb+9 without Bb? Since it's in D minor doesn't D7 suit better?
My ear tells me because of the 2nd voicing pattern, Bb feels better, and starting with a Bb is fine as the harmony is perfect.

The question sounds a little paranoid but I never had a teacher and I read&guess about all the theory I'd be thrilled if you can expand the explanation, thx!

Someone Explains These Chords To Me Plz~ Specific Issue Inside

I'm kinda new to music theory and don't have enough experience to understand this:

(Purple is keybord, guitar is ORANGE xD )

Tonic is E, and I think the main chords are Em D C by now. So this part of verse confused me.. is it D-Em-Em-D ?
Or it looks like kind of mixed using of D&Em, which makes it a vague paragraph to background the voice?
Or is it even Em11?
I just finished a book of music theory and try to understand this song logically.
Please tell me anything you come up with, I'm learning, thank you!

(The song is Let This River Flow by Soilwork)

How To Achieve This Effect?

What technique do I need to make this moist/sticky feeling?


I've upload a sample here:

Click

In this short particular part:

Click


It's in the very background. before every heavy pick there's a very viscous expression.. it's so cool. I want to know how to do it.
I've heard this feeling in many songs, can't recall them though..

sorry for my English I hope I explain well o_O

and yea this song is OP of Slamdunk ^^"