why are Do Re Mi Fa Sol La Si the standard notes?

Question

If you take an instrument without predefined notes, such as a trombone or a violin, you can produce an infinite amount of notes between Do and Re for example (applies with out of tunes instruments as well). With that logic, you could have an infinite set of 7 notes that are as evenly « spaced » as our current standard. Im sure im missing something obvious.

In: Physics

Answer 1

Then do re mi…..is relatively “new” from like the 11th century

They refer to the 6 notes of a hex-chord and not any one specific chord (usually a c chord is used)