TIL that the song Do Re Mi from The Sound of Music is in the key of B flat major, not C major, and that Do doesn’t necessarily mean C.

https://en.wikipedia.org/wiki/Solf%C3%A8ge

https://www.reddit.com/r/todayilearned/comments/161qzjb/til_that_the_song_do_re_mi_from_the_sound_of/