Vibrato is particularly strange in that it seems to require a lot of work, but in the end we all seem to find that the best sound comes when we relax and just let go. Unfortunately, hardly anyone can develop a vibrato without a lot of effort, but many of us get too caught up in it, creating a situation where we continue to force the sound with too much muscle and motion, never realizing a flowing, natural movement, and the stamina that using our natural mechanics inherently creates, the stamina we'll need to get through a piece, and eventually an entire concert.
One thing is certain, vibrato requires a lot of dedication to develop and master. In many respects, it’s not much different than a toddler learning to walk - incredible effort, hundreds of failures, and then one day, it's effortless... we think, "I want to go there," and suddenly we're running across the playground before we even consider how we're going to move our feet or our legs.
And, I'd argue that just like learning to walk, our bodies are actually built for vibrato, as awkward as it may seem at first. To make an important distinction, just like walking, none of our bodies are born already trained for it. Just like the toddler who graduates from her existence on the floor by pulling up on some furniture and eventually standing and walking with support, then balancing without support, then taking a first step and falling, and trying again, eventually making it to two steps, and so on, with vibrato we must recognize the importance of a progressive methodology, and cultivate the patience to see it through.
The #1 downfall of most students I've seen trying to learn vibrato is impatience. They see and hear others using vibrato and often even before they've sourced out an instruction video (and beware, there are some bad ones out there!), or their teacher has given some tips, they're tensing up their left hand, trying to wiggle as fast as possible on the string. Unfortunately, even with instruction, many students might get the basics, then decide they can't wait and just want to go for it again, tensing and wiggling wildly. Let's be perfectly clear: vibrato has nothing to do with tension! Sure, if we tense hard enough we can make our muscles shake in a way that could mimick a vibrato sound, but it's not a sustainable or healthy way to accomplish this critical bowed string technique.
A tense vibrato is also hard to control. While one-speed vibrato may be somewhat better than none at all, the goal is to create a vibrato with nuance to match the varieties of tempos and feeling we want to express in our music. Working with the natural range of motion of our fingers, wrist, and arm, we must train our muscles to pulse rhythmically at a variety of speeds and widths. Just like learning to stand, walk, and eventually to run, skip, leap, sashay, hop, and dance we learn how our bodies can work for us and then improve our efficiency and gracefulness over time.
The #2 downfall of students trying to learn vibrato is certainly having too much left hand tension to begin with. Students who grip the neck between the thumb and the base of the index finger, or press too firmly into the strings can't access smooth, fluid motion, or any motion at all. It's no wonder so many resort to trying to use even more tension to force some shaking!
Back to toddlers, isn't it interesting that none of them ever give up on walking. They might cry when they fall down, but seemingly only because they hurt or startled themselves, not because they had the kinds of common thoughts we might have when trying to learn vibrato, such as "I'll never get this," "Maybe I'm just not cut out for this," "What's wrong with me? Other people make this look so easy." I've never seen or heard of a toddler putting walking "on the back burner" as violin or viola students sometimes need to do when they've gotten themselves all wrapped up in frustration. We can't know for sure, but after crawling around for a while, toddlers all just seem completely convinced they must walk. They have places to go, people to meet, things to do, and perhaps most importantly, things they want to touch, hold, or eat that only someone a little taller or further away would be able to get to right now!
So, besides having a methodology and harnessing our patience, we might have an easier time learning vibrato if we focus not as much on the strange sounds we're making day to day, but the journey of it, and how vibrato will eventually make a difference for our music. Imagine how our favorite pieces will sparkle with vibrato, how we'll feel with this new dimension of expression, literally at our fingertips, and how much more professional and colorful our overall sound will be. All our efforts wiggling, shaking, and rocking for weeks and months on end are just a means to those ends, and the best place to start is wherever we are right now - recognizing that "all" it will take is training our muscles and joints to make tiny, consistent rocking motions with the least amount of effort possible.
Start with air violin and graduate only when you can easily make your wrist and/or arm pulse freely and rhythmically, but to such a small degree that you can barely see it moving. Next, spend some time sliding and gradually rocking in one spot on the string without adding the bow. Never press hard into the strings or grip the neck. Gradually add the bow and train for a variety of speeds and widths. And especially if you don't have a teacher helping you, or as a supplement to that instruction, consider joining the over 3000 students who have purchased and enjoyed my Complete Vibrato Mastery course here: https://www.completevibratomastery.com
Happy Practicing!