Question: The background of my question relies on the following points.

* Quine-Duhem thesis: it is difficult to test a theory with an experiment,
because the test would rely on other theories.
* The discussion of the previous point is difficult because we do not
have a "theory of everything", so it is not clear if the chain
of theories involved in an experiment ends somewhere.
* It could be nice to make an attempt to reverse the logic: imagine
a universe ruled by a given mathematical model (that we completely
know), including entities able to perform experiments, and try to
discuss to which extent they are able, by means of experiment, to
discover the rules.
* This approach does not require to mimic the real physical laws. In
the past, it has been tried to imagine very unusual hypothetical
universes and discus what the hypothetical inhabitants would see,
e.g., "Flatland", or the non-Euclidean geometries. In some cases,
scientists later discovered that the imagined universe had some relevance
for the real life.

Now, the question is: given a mathematical model of a hypothetical
universe, possibly including entities (animals, or robots) that are able
to perform experiments, how is it possible to discuss the results
of their experiments? And the models and theories that they can test and verify? Is
there any philosophical attempt in this direction? Can anyone suggest
some literature?

I do not think that these questions have a straightforward answer.

Just to avoid misunderstandings: I already deposited a pre-print on
this topic, with some thoughts in this direction, but without
references to literature. I do not put here the link because I do not
want that my question looks as an advertisement for my manuscript.

Answer: 
In addition to Nietzsche:

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[Rousseau](https://en.wikipedia.org/wiki/Jean-Jacques_Rousseau) wrote both the music and libretto for an opera - [Le Devin du Village](https://en.wikipedia.org/wiki/Le_devin_du_village).

[Rousseau - Le Devin du Village on YouTube](https://www.youtube.com/watch?v=Ld7XDELDnto)

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[Adorno](https://en.wikipedia.org/wiki/Theodor_W._Adorno) was a classically trained pianist, studied composition with [Berg](https://en.wikipedia.org/wiki/Alban_Berg) in Vienna, and wrote piano music and a number of string quartets.

[A selection of Adorno string quartets on YouTube](https://www.youtube.com/results?search_query=adorno%20string%20quartet)
Gabriel Marcel according to Brendan Sweetman composed music:

> 
> He also developed a keen interest in classical music and composed a number of pieces.
> 
> 
> 

However, I could not find a list of these compositions.

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Thanks to @sand1 from comments: "La Biblitheque Nationale Francaise list has a section for him as Compositeur(54) [data.bnf.fr/fr/11914394/gabriel\_marcel](https://data.bnf.fr/fr/11914394/gabriel_marcel/)"

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Sweetman, B. "Gabriel Marcel". Retrieved April 23, 2019 from *Britannica* <https://www.britannica.com/biography/Gabriel-Honore-Marcel>