Should mention Open Sound Control which is also pretty good. Not exactly a competitor, it was supposed to provide a richer, real time interface. Still popular for certain use cases, including beyond music.

Concepts like Reactive programming are widely used in web/UI contexts. The problem of connecting a UI to an underlying data set is not trivial. Several frameworks deal with this.

As was already said, concerns like Accessibility are studied academically. They have more to do with user experience than the technology, so not sure if they match your question.