First and foremost, I'm a mix of mixes.
My first mix consists of what I have one, and what I have seven
What is subject to change,
The result of eels and a madman.
After that, I am a mix of love and music
Of grace and agility,
Of shaking and screaming.
My last is a mix of everything
Multitudes of genres
And yes, the answer is one.
It's abbreviated to 3 letters.
Hint I:
what I have one, and what I have seven: look at that blue box.
Hint II
The result of eels and a madman.: think
MarvelSpiderman
bar tbyq naq frira fvyire onqtrf (rot13)
$\endgroup$ – tmpearce Dec 5 '16 at 17:17