I've played guitar for over ten years, and my alternate picking really blows when it comes to fast stuff like 7 to 10 notes per second range. I sometimes wonder if I have reached my natural limits? what can I do to progress?
A lot of alternate pickers get stuck right where you are, and it's because fast alternate picking requires a very specific technique—one that no one even understood until a few years ago.
The world's foremost expert on speed picking is a guitar educator out of New York named Troy Grady. In his online video series Cracking the Code, he has made the first truly thorough and systematic analysis of how to play fast on picked instruments. He did this by studying slow motion footage of super fast players, in jazz, country and especially the rock shredders that he grew up with. (Mad props to Troy for having the patience to watch 80's speed metal instructional videos at 1/10 speed over and over and over...)
Troy's big idea is what he calls "downward pick slanting." It's a simple concept: you tilt your pick toward the floor, so that every stroke makes a nice, easy, straight line, and because of the diagonal motion you never hit any other strings by accident. Most fast players do this, whether they realize it or not.
Once you get used to this, you can play incredibly fast, and it feels glorious. Your right hand moves through the strings like a hot knife through butter. But there's a catch: when you want to switch strings after a downstroke, your pick is buried in the strings. So unless you're careful, you will need to make some complicated motions to get to the next string and your speed will crash and burn.
Players that use economy picking, like Jimmy Bruno and Yngwie Malmsteen, solve this by just sweeping through to the next string. This works for ascending lines, where the pick is already planted down on the next string, ready to sweep through. For descending lines, that isn't an option, so they often "cheat" by using hammer ons and pull offs to make sure they never have to change strings after a downstroke while descending.
With alternate picking, you have a bigger problem on your hands. When you just played a downstroke and want to move to another string, you can't resort to sweeping, so what do you do? The solution is what Troy calls "two way pick slanting." On the last stroke before you switch strings, you turn your wrist just a tiny bit, so now your pick is slanting upwards and you escape from the strings instead of getting buried. Every time you're playing the note before a string change, if you're about to get buried, you rotate your wrist so the pick slants the other way. This sounds like a lot of mental math, but it's something your hands learn to do automatically. Understanding what's going on just helps you learn it faster. Two way pick slanters include Al Di Meola, Chris Thile and Paul Gilbert.
There are simpler ways to do alternate picking at speed, but past about 10 notes per second, two-way pick slanting is pretty much the only game in town. The only other option is using hammer-ons and pull-offs, or re-fingering your lines to avoid inconvenient string changes.
If you want to learn more, Google "downward pick slanting" and "two way pick slanting." But the best explanations are still in Troy's videos. The whole series is well worth watching.
For electric guitar, you can add a fair amount of speed by just knowing that you do not have to pick every note. When you start adding meaningful hammer-on's and pull-off's you can add a good amount of speed.
Try just adding certain hammer-on's to you box shapes when you practice your scales. For the pentatonic scale for example. Pick the first note and then hammer on the second one (On each string)
For scales with three notes per string. You can pick the first and then either hammer on the other two notes on the string or pick the third one again.
This will all lead into your legato phrasing technique as well as add speed. I would at the very least alway want to hammer the last note you play before you change strings as this will give you the chance to get your right hand to the next string without there being a pause.
Remember to take care to work on your economy of motion.
Alternate picking has its limitations. In my humble opinion, the further development in that area requires (paradoxically) abandoning the alternate picking in some situations. Please check the concept of "economic picking". Most very fast players do not use alternate picking all the time (for example it would be impossible to play very past arpeggios using only the alternate picking). I assume that practicing sweep picking will be very helpful in your situation.
Try looking for sweep picking, there's a great method created by Frank Gambale about it.
Just try not get addicted, 'cause this technique makes you play very fast, and playing fast is NOT as equal as playing beautifully.
The thing about Paul Gilbert, Yngwie Malmsteen and other guitar gods, is they have a pick angle thats approx. 45° clockwise. It causes your picking to be more soft (there's also the thing that they don't put much pressure on the picking in order to gain more speed).
Malmsteen has this video:He says something about his picking here.
But there's a lot more, just search and you'll find.
I think I am in agreement. I have never been able to figure out how to get fast alternate picking from string to string to work properly anyway. What I have developed is more of a natural flow between picked notes and hammer-ons/pull offs. I think all guitarists understand this and play by feel. I can get most of what I want to play across anyhow, trying to get alternate-only picking must have some rewards in it but for the most part I can construct solos across most chord arrangements that sounds good without the need to alternate pick every note. I think it's a combination action...a little alternate picking, a little hammer-on/pull off, a little sweeping, a little economy picking. How it's done is something left up to the player and how it feels naturally. Learning your scales and modes and memorizing them on your fretboard combined with a combination of picking styles will ultimately lead you to being able to play almost anything against any progression.
Not knowing what "alternate picking is" but being able to flat pick pretty well, I can tell you what I used as my speed model. I am a violinist, and we are sometimes asked to play termolo. This is VERY fast back and forth with the bow, and comes from the wrist. I can't imagine needing to play faster than that, and if you are picking from the elbow, that would slow you down. The above comments about hammering and picking are right on.