The composer runs those four notes throughout the symphony. They occur mixed in various musical phrases, but they keep their basic character.
Symphonies are relatively long pieces of music, usually complex, and usually played by big orchestras. If you go to hear a symphony, you also get a visual complex: Bows and fingers playing strings, drumsticks on drums, symbols clashing, woodwinds and brass being picked up and rested, then picked up again. There’s activity on stage, and it all moves to the baton of the conductor in the notes of the composer. All that movement is a sitting ballet, typically in black and white, with all the color in sound.
You, too, are a composer. You take a few notes and turn them into a personal harmony that evolves on your basic notes. Here or there you add notes or change the tempo or key, but those basic notes stay the same. They are the notes that others remember. Very rarely do others remember all those complex motifs and developments. When they think of you, they hum the basic notes of your makeup. Only you can play the complex symphony.
But that also applies to your humming the life of another. There are the recognizable basic notes, the motif on which the composition of a life is built. Those are easy to remember, so they stay with you. Those notes become an earworm, but the rest of the symphony? Well, usually it’s lost because it’s complex, and you have enough to do trying to play your own symphony, let alone trying to hum someone else’s.
So, we simplify the lives of others, reducing them to some basic four notes. They are important notes, we note, but they are no more the whole complex of a life than your basic four notes are the whole complex of yours.