sketches

Yesterday I spent the whole morning watching music videos on youtube.com, trying to capture the characteristic movements of female singers such as Madonna and Björk.
I was in a creative dip and these excercises are great to recapture the feeling of what it is all about (in my opinion): looking and keep looking at people. How they move, how they are dressed etc.
I'm not joining a class, but this is almost as good.
Oh, By the way:does anyone know from which videos these sketches are?