I'm using music21 to generate score fragments on the server-side and Verovio to render them on a browser. Which works ok.

Now, I'm trying to do some more elaborate things with the SVG output: change certain note colors, place extra svg elements based on score elements positions, things like that. An example: drawing a bracket given its musical position (like from measure 1 beat 3 to ...) -

score example

The problem is that the promising docs (here & here) are blank :-(

Any ideas or working examples?