In the history of American Blues music, what part did hollars and calls play in the development of the Blues?

This is some random question my teacher asked me. I cannot find it anywhere!

Learn To Play Blues Guitar

It is not that easy to pull out a definition of blues. You can tell that Robert Johnsons’ Rambling on My Mind or B.B. King’s Everyday I Have the Blues is definitely blues, but what about van Halen, Al Di Meola or Pavarotti’s songs?
Of course, you could define the blues by the call-response structure, the [...]

5 Killer Tips to Play the Blues Guitar Easily – 12 Bar Blues Guitar

If you want to play Blues guitar there are many different methods to choose from, even hundreds of them. The style has many variations and is the most traditional and well-known forms of music in the world. It would be too difficult to exactly describe how to play blues so instead here are a few [...]