Today marks the fiftieth anniversary of the March on Washington, the massive civil rights protest at which Martin Luther King, Jr., famously delivered his “I Have a Dream” speech.

That speech’s stirring vision of political and social equality for blacks is now legendary, but its dexterous musicality is often overlooked.

The New Yorker‘s Page-Turner blog takes a second listen:

After Mahalia Jackson’s call and shout—“Tell them about the dream, Martin”—King threw down his prepared remarks. Before long, he was sampling from an array of sources, skipping from the “I Have a Dream” refrain to Isaiah’s vision…and blurring the boundaries between oration, sermon, and song.