"who bared their brains to Heaven under the El and saw Mohammedan angels staggering on tenement roofs illuminated,
who passed through universities with radiant cool eyes hallucinating Arkansas and Blake-light tragedy among the scholars of war,
who were expelled from the academies for crazy & publishing obscene odes on the windows of the skull,
who cowered in unshaven rooms in underwear, burning their money in wastebaskets and listening to the Terror through the wall,"

Ginsberg said that he modeled this poem after the work of the jazz artist Lester Young, who employed all those old jazz tricks of repetition and improvisation. In it, Ginsberg complains about the costs of a stifling, post-war culture for young American men—all while using the repeated word "who" as an anchor for his increasingly troubling observations.

It's obvious from this passage that his expensive education didn't have the "desired effects" on him and his buddies. They hallucinated Arkansas, and ended up in their underwear burning money. All of Ginsberg's exciting imagery here poses the question: Are the traditional ways of gaining knowledge doing more damage than good?

With this poem, Ginsberg became the guru of the counter-cultural revolution.

Ginsberg keeps time in this poem with the word "who." When he reads it out loud, this word acts as the anchor around which his improvisational observations take place. So "who" becomes just like the repeated phrase in a jazz improv.

In "Howl," though, Ginsberg goes on to describe his friends as they negotiate the different landscapes of their shared cultural hell. But the "who" is what binds all the madness together. While the poem threatens to pull apart at its seams, this one repeated element helps Ginsberg keep it together.

Sort of. As much as the Beats ever really kept it together while burning it all down, you know?