How do you express what cannot be said?

This is a beautiful quotation.

But now I'm giving it some deeper thought.

Really? ... "what cannot be said" ... what is it that cannot be said that music can express?

I would love to hear your ideas, because there are some incredibly eloquent writers and speakers whom I admire hugely, and I cannot help wondering what it is that they cannot express that music can...?

And add to that the criterion ... "on which it is impossible to be silent"

Do comment!

Another thought that occurs to me is that we use images as we speak sometimes, and they add a new dimension to our spoken words.

What is the role of music here? Would it add a dimension, or speak for itself?