By Jove, I think she's got it!

I figured it out! Somewhere in my mind, The Red Wheelbarrow became juxtaposed with that other poem by William Carlos Williams, The Dance. When I re-read the latter poem just now, it reminded me, of course, of the dancers rocking out in front of the New Riders. I have now successfully yet inexplicably linked The New Riders of the Purple Sage to William Carlos Williams. Phew! I thought I was going crazy.