When people try to play heavy metal gallops, it's really common for the picking hand to tense up. Instead of a clean, even down up down, you get a sort of smeared, rolled sound.
There are probably loads of causes, but in my opinion there are two that matter most. Here's what they are and how to practise your way out of them.
Reason one: you haven't built the strength yet ▶ 0:44
First off, it's just muscle strength, and that only comes through repetition. There's no way around it. If you play a gallop, start to speed it up and your arm tenses, there's a very good chance you just need to build some strength, coordination and dexterity in your picking hand.
The way you get that is sheer repetition: playing the gallop and gradually building up speed. I'd like to assume you're putting the time in, but a lot of people aren't. So do put the time in, at least 10 to 15 minutes a day of just playing gallops and speeding them up.
Reason two: your picking motion is too small ▶ 1:33
The main issue I see with my students is that they keep their picking motion too small when they're doing gallops.
Now, you might think a smaller movement means more efficiency, and you'd be right. But if you're getting that efficiency at the expense of a good sound and relaxed, fluid playing, what's the point?
When you keep the motion small and tight, you end up almost rolling over the string, and that's the problem a lot of people seem to run into.
The fix: exaggerate the range of motion ▶ 1:50
Take your gallop and increase the range of motion across the string. You can be quite dramatic with it at first. Then start to speed it up.
As you get faster, it's going to be tempting to close that distance in. That's probably how you'll naturally play once you're comfortable with the technique. But for now, keep the range as wide as you can.
Think of it like resistance training. You're making the pick travel further in the same amount of time, so you have to work a bit harder. More importantly, with the wider motion you get a nice clean down up down that sounds even.
Sometimes we just need to reset the way we're doing something before we step back into our old habits, having reframed them slightly.
This is just a practice tool. It might be inefficient, but if it forces you out of that tensed-up position, there's something really useful in it. If you can train yourself to play fast with a wider motion, you should be able to move even faster once you rein it back in. It's a simple prompt, but it forces you to relax a bit more. And it still won't work unless you put in those 10 to 15 minutes a day.
Warm up first ▶ 3:31
Another important thing is just warming up. Even over the course of recording this, stopping and doing a few gallops every now and again, I got faster and more consistent, simply because my arm was warmed up and moving more freely. So don't judge your gallops on the first few seconds you pick up the guitar.
Bonus tips: pick angle and the upstroke ▶ 3:50
Two more small things to experiment with.
The angle you strike the string at. Some people prefer to cut into the string a bit more. Others turn the palm a little and almost pick away from the string. Different people prefer different things, and honestly I couldn't tell you which one's better. Try both.
Give the upstroke as much attention as the downstrokes. A gallop is down up down, then down up down again. The upstroke in the middle needs just as much force as the two downstrokes, or the rhythm goes lopsided.
Go and try it
Set aside 10 to 15 minutes a day for gallops. Warm up, then play them with a deliberately wide picking motion, and nudge the speed up with a metronome while keeping that motion as big as you can. Let it shrink naturally as you get faster, and keep an ear on that upstroke.
