I do think it's a good idea to have a dramatic change of some sorts though within a song, whether it be a different key or tempo, especially after the second chorus before the 3rd chorus, because after you do the 1st two chourses the listener knows what's coming and they are getting bored, but play something different from the rest of the song, and then they forget about the chorus for a minute, and then when you take them back to the chorus the 3rd time they are excited to hear that familiar territory again. Enter Sandman is a good example of that technique.
But I meant in my original post to always write all instrumentals in E or E flat.
I mean when you are in E, but then play the harmonic minor in A, it's really the Phyrigian, so that's sort of like going from E to A within a song, but I just see as it going to a mode.
But, just seems like a waste of time/energy to master all the scales & modes and arpeggio patterns and sequences etc in every key, when it seems like E or E flat is most often used for shred instrumentals.
I guess kinda like how C seems really popular for Piano.
I mean I know it's only a matter of moving the shapes down another fret to go from key of E to F, but still, I'm just trying to think in terms of being the most efficient as a guitarist/composer.
You know kinda like the train of thought, not much use in mastering all the Jazz chords if you are a shred head, yeah sure maybe you could throw a few in there to be unique somehow, but really that time could be better spent truly mastering something that you could use 99% of the time.
I'm looking at it in terms of not being a well rounded musician, but instead being a true Master at a very small niche style of playing/composing.
Basically, Yngwie Malmsteen of course.
And I haven't analyzed all of his songs, but I'm curious to how many of his songs are not in A or E. (yeah I know A flat or E flat because he tunes down.)
But just as a few have already pointed out, to always write every song only in a specific key of E and no songs in other keys, can start sounding similar, and I have read many people write that Yngwies music starts all sounding like the same song over and over after awhile.
I think Yngwie mostly plays in the key of E, maybe also A sometimes unless I am wrong.
But people like Vai probably utilize every key often, and maybe that's why all of Vai's songs each sound so different from each other.
But at the end of the day, I am aiming more for the Malmsteen approach, whatever he is doing, more so than anything else.