This occurs the day that Nick, Jordan, Gatsby, Tom and Daisy go into New York City and take a hotel suite; the wedding march is playing downstairs, and causes Daisy to feel nostalgic for the day that she married Tom. She remembers the same wedding song, and she remembers that it was very hot that day, much as it is hot this day that the group goes into town. There is also a certain sad irony, because Daisy is in the hotel with her husband and the man she probably loves more, Jay Gatsby; yet there will never be a wedding march for Jay and Daisy, despite his continued efforts to win her over. A wedding song such as this is supposed to herald a new beginning for a bride and groom, but in this case, it is getting close to an inauspicious end for Gatsby while Daisy is going to reconcile with Tom by the end of the day.
Fitzgerald's reference to Mendelssohn's wedding march is a deliberate form of both dramatic and situational irony at this particular point in the novel. Dramatic irony occurs when the reader is aware of something that a character or characters do not know. At this juncture, the reader is mindful of the fact that Jay Gatsby and Daisy Buchanan are having an affair. Tom, Daisy's husband, is suspicious but has no definite proof. All that he knows is what he has seen. Earlier, at their home, he saw the look that passed between Daisy and Jay, as the following extract illustrates:
Their eyes met, and they stared together at each other, alone in space. With an effort she glanced down at the table.
“You always look so cool,” she repeated.
She had told him that she loved him, and Tom Buchanan saw. He was astounded. His mouth opened a little, and he looked at Gatsby, and then back at Daisy as if he had just recognized her as some one he knew a long time ago.
When they are about to leave for Tom's apartment at the Plaza Hotel in New York, Daisy insists that she wants to drive with Jay in Tom's car. When she accompanies him to the vehicle, her intimate gesture clearly indicates her fondness for Jay.
She walked close to Gatsby, touching his coat with her hand.
Tom sees what she does and is clearly upset. He asks Nick and Jordan if they have seen, but they act dumb.
Situational irony lies in the fact that the circumstances, conditions, and actions of the characters indicate the opposite of what one expects. In this situation, the reader also knows that some confrontation is about to occur, since Nick alludes to it at the beginning of the chapter. A confrontation is the last thing one would expect at a wedding.
The situational irony also lies in the fact that weddings typically indicate the beginning of something good for the couple involved. They have made a commitment to each other, but Daisy and Tom, although married, have strayed from their vows. Tom has had all sorts of affairs, and now Daisy is also committing adultery, which is not good at all.
Fitzgerald could have used a reference to Richard Wagner's similarly famous "Here Comes the Bride," but he decided to use Mendelssohn's composition because not only is it used for weddings, but it is also sometimes played as the recessional in church services. The recessional is usually the hymn that ends the service.
On another level, therefore, the composition ironically signifies not only the beginning of a new association (for the couple downstairs) but also the end of another. It signifies the end of Gatsby's dream on this occasion. During his confrontation with Tom in this chapter, Gatsby realizes that he has lost Daisy, his one true love, as the extract below indicates:
But with every word she was drawing further and further into herself, so he gave that up, and only the dead dream fought on as the afternoon slipped away, trying to touch what was no longer tangible, struggling unhappily, undespairingly, toward that lost voice across the room.