First, I always urge everyone to check out all the great tutorials by Fiddlerman! 

There's been a few masterclasses I also find extremely helpful.

Was working on my intonation & remembered a GREAT tip I from a Masterclass (just don't remember which one, at the moment): 

💥 Don't bother trying to correct an 'off' note without playing the note that comes before it!  The idea is to understand the interval between the 2 notes played is just as important to learn & get right as the correct pitch!  

This is GREAT - Pinchas Zukerman shows 'articulation' comes from the BOW - it's NOT all left hand: 

https://youtu.be/HACjYCZejD8 

What I've learned from this masterclass on vibrato, is I have to just let my thumb loosely go to where it needs to be (for a little support) and not obsess about it - so I can concentrate on the vibrato speed and width.  I like the expressiveness and I'm still working on it, to make sure my bowing & intonation don't go out the window in the process.

https://youtu.be/nynKUmt262s 

I posted these videos elsewhere, but I feel pretty strongly that if bowing isn't straight - it's hard to progress with anything else on the violin, or viola.  ...and think everyone can get sloppy once in a while - maybe forget how important bowing really is:

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