4.1212 What can be shown cannot be said.
OK, but is this a stipulation about a possible concept-script or a grammatical truism (like “colors cannot be spoken”)? Or something else? Cf. Schopenhauer on music: We could “just as well call the world embodied music as embodied will.” (WWR, v. 1, §52, pp. 262-3)
Music, like the phenomenal world, shows, as it were, the nature of the thing-in-itself. What this is cannot be said or translated into concepts. Nor can it be demonstrated or proved that music does this. The listener must simply hear the music and agree that it expresses the inner nature of the world. On that idea cf. the preface, where LW talks about being understood only by someone who has already had similar thoughts.