Earlier quoted context omitted.
We call it "solfège".
Akshually... According to Wikipédia FR, the French equivalent of Sight Reading is "Lecture à vue" [1]. Notes: - I'm French; - I learnt to play the piano as a teenager, and I'm trying to get back to it again as at 45+; - I too discovered the "sight reading" term online, but that was long ago (as I recall, through a video of an adult piano player doing "live sight-reading" versions of songs he didn't know beforehand, s…
Though I wouldn't say that it is the same as "sight reading" -- but maybe "sight singing"?