The Big Apple. The Capital of the World. The City that Never Sleeps. There's a reason that New York has so many nicknames: it's so awesome that one nickname just isn't enough. "Man Listening to Disc" is a poem that describes the narrator walking through the famous streets of the city. We get a lot of the sights and sounds of New York: the pigeons, the pedestrians, 44th Street, Sixth Avenue. This is significant, because the music that the speaker is listening to—jazz—is very closely associated with New York. Jazz exploded, after all, during the Harlem Renaissance in New York in the 1920s. So the poem sets up a link between the music and the city itself. New York is not only the Capital of the World, it's the Jazz Capital of the World.
Line 2: The speaker tells us he's walking along "44th Street." If we know New York well, we'll know that 44th Street is in midtown Manhattan, which is in the heart of the city. The speaker is right in the middle of things.
Lines 32-36: We're getting more geography in these lines, with the speaker announcing that he and his jazz musicians are going to "angle over" to the "south side" of the street and then turn at "Sixth Avenue." Sixth Avenue is a famous avenue in New York. So here, again, the speaker is locating us in New York City. And that's important because New York is a major capital of jazz music.
Line 46: The speaker hopes that he'll "eventually make it all the way downtown." "Downtown" and "uptown" are two terms that are very commonly used in Manhattan, New York, to refer to the south and north sides of the island. So here again the speaker is using geographical terms that locate us in New York City. These geographical references remind us of the deep relationship that jazz has to the city.