This tutorial is helpful because it shows he steps clearly, quickly, and in a way students of any age can understand. It is also nice that it is in a home setting, not a shop.
This tutorial is well done. She explains the basic movement needed to start vibrato, uses close-up screen shots so that the viewer can see exactly what her wrist and fingers are doing, and shows the progression from beginning vibrato to more advanced vibrato. She also explains what beginning student vibrato should sound like. I think this is a great video for students who are starting to learn vibrato.
This "tutorial" was actually the unedited taping of a class instructing djembe students how to play slaps and tones on djembes. The information is great, and of excellent quality. However, the video needs some major editing and the instructor is very hard to hear.
The tutorial was well done with good practice tips, and moved along at a decent pace. The one thing that I didn't like was that there was no talk about color or dynamics while playing and practicing.
I think she does a good job of explaining and demonstrating how to vary dynamics on the violin. The only negative is she has a tendency to over explain, but it is still a great learning tool and some beginners may need the over explanation.
This tutorial is ok, there are some steps hat he has overdone (and made much harder than they need to be) but for the most part this is a good idea of what is involved.