I think it should work for facts, but I haven't personally tried much of that. Right now, it doesn't make a distinction in how it schedules each type of question. I have an update coming that should make it way easier to play with it for this type of purpose. The changes are still not in a formal release, but they are in master and the docs at https://trane-project.github.io/generated_courses.html should give you an idea of how it will work.

For music practice, I find it really helpful. Simply knowing the next thing you should practice without having to think about it too much is very helpful. I find it easier to practice for longer without getting bored as easily. If I get frustrated with something, I can get another question very easily. I find myself not realizing half an hour or sometimes more has gone by, which is not the case as often when I don't use it.

Interesting ideas for how to write the cards. But the dependency part seems to be limited to letting you pick questions from a subtree. SuperMemo has something similar, which is the closest I was able to find in existing solutions.

The problem is that this basically means dependencies can only form a tree, with one topic depending on only in at most one other topic. What I wanted was something that let me express the relationships as a directed acyclic graph. Something like learning a big chunk of a music piece is dependent on the questions for learning individual smaller passages. Something as basic as that cannot really be expressed with a tree but is trivial with a DAG.