When Biden seemed lost at the beginning, it was the Introitus.
When they were arguing about golf, it was the Confutatis.
When they were both responding to how to help Americans with addiction by talking about restricting fentanyl coming into the country, it was the Dies Irae.
The entire thing was underlined by the Lacrimosa.
The closing statements, the Kyrie. Lord have mercy.
Edit: (Obviously these are not in performance order.)