Question

How did blues musicians alter the major scale to emphasize feeling and emotion?

Answer 1

Blues, secular folk music created by African Americans in the early 20th century, originally in the south. The simple but expressive forms of the blues became by the 1960s one of the most important influences on the development of popular music trogouth the United States.  

In the context of the question many authors explain that the blue musicians use a lowered 3rd and 7th and add a raised 4th to emphasize and emotion.

Answer 2

They lowered the third, fifth,  and seventh scale degrees to create blues tonality.