Listen closely to Sir Paul's voice as he sings. He's singing for a departed friend, Jimmy Buffet, and is skating at the edge of breaking down in tears. But he manages to hold it together. See this post, Paul McCartney on Emotion While Performing.
I discuss this in my book on music, Beethoven's Anvil, pp. 97-98. In the opening paragraph I'm reforming to a performance where Midler was at the edge of tears singing "One More For My Baby" for Johnny Carson:
Let us recall Bette Midler’s performance for Johnny Carson’s farewell. Instead of thinking about how that performance affected us, we might wonder what it was like for her. I recall that her eyes were teared over. That suggests that she may have been skating on the edge of an impulse to cry.
I have had similar experiences while performing on my horn. Tears would well up in my eyes and I could feel a lump in my throat. If I gave in to the impulse I would be unable to continue playing. But if I tried to suppress it completely, the magic would be gone and my playing would become ordinary. I learned to bear down in my chest and abdomen “just so” and skate on the edge. The feeling didn’t disappear, but I could continue playing my instrument.
We’ve all had similar experiences quite independently of music. Imagine you are in some public place and you receive bad news, perhaps about the death of a loved one. You are stricken with grief and feel a strong impulse to cry. At the same time you feel a contrary impulse to remain reserved in public, to suppress the sobbing and the tears. Later on you are called upon to deliver a eulogy at the funeral. Once again you are torn. In order to speak intelligibly you must remain in control of your vocal apparatus. But you are speaking of your dead friend and so are also moved by a grief that wants to commandeer the same muscles in the service of crying out.
