(I'm not in the music world but need to know the answer for esoteric reasons.) The image above contains excerpts from one of Stravinsky's pieces. I assume in score writing is it commonplace to notate the different sections of the piece in order to break the piece up. What is the name of these numbered boxes? Are the annotated "number in boxes section markers" a standard symbol in sheet music with a name, or were they only something Stravinsky used with the symbol varying?
The Sibelius app (and presumably the wider world) calls them Rehearsal Marks. If the boxed values are numbers the conductor will say "play from figure 5". If they are letters the conductor will say "play from letter B". I've never heard them referred to as sections (but my experience only covers band, orchestral, small ensembles and choirs) so other music may use the term "section".
Bar numbers - if they are sequenced to each bar. The other marks are section marks, usually letters. Often called 'rehearsal marks'. It's so much easier in rehearsal to 'go from a bar before section C', or 'play from the anacrucis in bar 16'. Could be that Igor chose section numbers in preference to letters.
My brother was a composer, and he usually used this marks to differentiate between themes in a piece.
For example, he marked the introduction with an
Intro mark; then, when the main theme began, he usually put an
A mark; then, when he wrote a second theme, he put a
B mark, and so on. The marks had nothing to do with the bar number.
I've heard those marks referred as "theme marks" or "rehearsal marks". They become useful when rehearsing (e.g. "Let's play theme
B), or when explaining that a single piece is "divided" in two or more "themes".