Music expresses that which cannot be said and on which it is impossible to be silent.

[Ce qu’on ne peut dire et ce qu’on ne peut taire, la musique l’exprime.]

Victor Hugo (1802-1885) French writer

William Shakespeare, Part 1, Book 2, ch. 4 (1864) [tr. Baillot]
    (Source)

(Source (French)). Alternate translation:

Music expresses that which cannot be said, and which cannot be suppressed.
[tr. Anderson (1891)]