Will I ever prove that I exist? What do I exist as?

I may try and be a shadow to you
trying to protect you from the scorching heat,
but will I ever know that you're a night wanderer?

I may try to be the rainbow
for the silver lining in your storm,
but will I know that you constantly live in a drought?

I may even be a nightingale
filling your ears with music divine,
but when will you tell me that you are deaf?
Deaf to my yearnings and my cries,
and blind towards the tears
that wouldn't come out of my eyes.
Deaf to the rhythm my heart beats for you,
And yet I keep making the music.
I keep making the music.

I keep making the music,
perhaps to prove that I exist.
But what decides existence?
Do I exist?

I exist in nostalgia,
when people remember their first true loves.
I exist in memoirs,
of the greatest rivals they made.
I exist as the guidelines,
of the way they shouldn't live their lives.
I exist in their sensations,
illuminating how comforting a touch should be.

Yet I need to prove that I exist.
Why?