The 60's and 70's brought about significant changes in the kind of music being written by composers. This was partly motivated by advances in technology. There was a growing influence of non-western cultures. Composers were also turning away from traditional institutions and schools of thought for leadership and artistic vision.
I worked with fellow student Ethan Helm to create a short presentation on Minimalist Composers of the 60's and 70's. He is a saxophonist and composer and knows a lot more about music than I do. Collaborating with him on this was educational. You can find the presentation here.