I always advise my students to practice new licks, rhythms and techniques slowly. I provide slowed down jam tracks to help with that. Nearly always this is met with some degree of resistance. Often along the lines of “Well, I want to be able to play it full speed so I should practice it that way.” Or “Playing it slowly is boring and doesn’t sound as good.”
To address the first point, of course the goal is to play at full speed, or any speed you want, but you need a strategy to get there. When we’re trying to do something new we’re asking our bodies to do things it’s not used to doing. With the harmonica this means using muscles we’re not used to using – we may be using muscles we didn’t even realise we had conscious control of – to make minute adjustments. Learning to do this takes time. You need to break down the process into smaller pieces and go little by little. By practicing slowly, you give your new skill time to develop. When you can do it slowly, accurately and with confidence try ramping the speed up gradually. You’ll be suprised at your increased ability to handle the higher speeds. Of course that’s not to say you’ll magically be able to play complex licks at blistering speeds, but you’ll have built a solid foundation which you can more readily build on.
As for playing slowly being boring or not sounding as good. That might be the case but you’re doing it for a reason, and believe me you’ll feel and sound good when you’ve mastered it.
In case you think this is just me going off on one, try reading this great article: 8 Things Top Practicers Do Differently. It’s an examination of an experiment in effective practicing. There’s a lot of solid findings there, but the single, takeaway piece of advice is:
The top performers utilized a variety of error-correction methods, such as playing … just part of the excerpt, but there was one strategy that seemed to be the most impactful.
Slowing things down.
After making a mistake, the top performers would play the passage again, but slow down or hesitate – without stopping – right before the place where they made a mistake the previous time.
This seemed to allow them to play the challenging section more accurately, and presumably coordinate the correct motor movements at a tempo they could handle, rather than continuing to make mistakes and failing to identify the precise nature of the mistake, the underlying technical problem, and what they ought to do differently in the next trial.
So please, if you want to get good (I want you to get good) slow down. It’s not sexy, but it works.