She reminds him of music, the art itself.
She is as perfect.
She is as brilliant.
She is as mysterious.
She is as miraculous.
Sometimes she is as tragic.
The depths of her heart and soul are as immeasurable.
The fire burning within her is as fierce, as eternal.
Just like the mere existence of music beautifies the lives of many, her mere existence beautifies his life. In all possible universes, in all possible planets, in all possible constellations, in all possible galaxies, she'd always be the equivalent of music to him, or even more so. No chord could ever sound like her voice, feel like her touch, taste like her mouth or smell like her skin. To him, she was greater than music.
Just like the mere existence of music holds a healing power against all kinds of suffering and pain, her mere existence is the solely source of his strength; his steel-like skin, all of his supreme skills - none of those things would serve their purpose if he was missing her. The rhythm of her heart beating close to his is his favorite symphony.
Just like music is other men's antidote, she is his.
Just like music is the answer to a million questions daily asked by humankind, she is the answer to all of the questions he could ever ask.
Just like music is one of humankind's greatest treasures, she is his.
Friedrich Nietzsche once said without music, life would be a mistake.
He knew too well that without her, life would be a mistake.
Humankind could never survive without music.
Clark Kent could never survive without Lois Lane.
She is, to him, as necessary as music, for without her everything would be nothing but a tragic mistake.