Conductors can write notes about certain parts that can be accessed by musicians. Opera musicians (where different people play the same music every night) can have their own personal notes.
Most exciting is ofcourse that everyone has instant score access. That removes a shit-tonne of time wasted during rehearsals.
Those are just traditional use cases. I'm excited to see what will come. I don't know ifusic as it is practicedtoday can be "expanded" in any meaningful way, but that only time will tell