The video of Ben Eller that @tommo posted is awesome. Great vibrato tips. I ‘speed watched’ it so maybe I missed it, but I didn’t see him address adding vibrato to a bent note though. Bent-note vibrato is hard.
Here are some ways to get good bent-note vibrato happening that I found really helpful over the years.
Mechanic:
The forearm needs to be rotating and driving the movement when you’re applying vibrato to a note that’s bent. What Ben Eller calls the ‘wrist’ vibrato might have some wrist involved, but this is primarily a forearm rotational movement. Please someone correct me if I’m wrong, but I can’t think of anyone with awesome vibrato (in the bent-note context) that doesn’t have the forearm as the driving force of the motion.
String Tension:
One thing that helped me a lot was doing a half step bend since there is less tension. Just to keep it simple, I’d practice the vibrato as a series of semi-fast half step bends and releases. Once you get that going, move onto full step bends. Then 1 1/2 step bends. They’ll all come in the music we play so we need control over each, plus the sheer variety helps with the motor learning.
Another thing that will help fighting the tension of the string is to bend near the middle of the string, which will always be at the 12th fret lol!!! We of course need to be able to bend anywhere, but if you just want to master the technique we need to find the easiest way to do it, then build on that base. So the easiest way to start would be bending the 12th fret 1/2 step.
Speed:
I’d try vibrato at a bunch of different speeds to help with control. Plus, depending on the context, the vibrato should be appropriate regarding its speed. I remember practicing intentionally trying to make the vibrato sound like 16th notes or triplets. This was all just to get the feel of it though. We of course shouldn’t really need to think like that when we’re playing real music.
A good goal, just off the top of my head, is to try to make a vibrato sound like triplets at 120 bpm. That’s a nice usable vibrato. It isn’t sea-sick chorus-y slow, and not Kirk Hammett screeching dying cat fast. I feel like this is analogous to when we pick, finding a speed above the threshold of where string hopping is possible. If you can do a vibrato at 120 triplets, you’re probably not going to be able to do it with an inefficient technique.
Lastly, this isn’t a ‘lesson’ because there’s no instruction, but I can’t think of anyone with more command of vibrato than the great SRV, and here’s a song where he does many different types of vibrato, both bent and unbent:
Plus, doing that with 12’s or 13’s or whatever he played with…damn.