Really nice! I would love to add all my notes here, but I sometimes needs to include images, and this is a blocking feature for me. Any plan to include that?
A really nice to have would be to have inline Latex mathematical formula, but it may be too specific for your app.
A short optional sample of every composers and songs would be nice, just to get an idea of the music. I can't remember music in my head (kind of Aphantasia for music), so it's really hard for me to choose just from the list.
It doesn't have a good accuracy. I have yet to see a real-life dataset where it's better than to just call LogisticRegressionCV from scikit-learn. For bigger datasets, you may use vowpal wabbit or Fasttext. It may be a little bit slower for the training (but not so much), and as fast as LR for the training. What is the purpose of using an algorithm when another one is just better?
Does anyone have a good book for advanced linear algebra? I learned the basics in school - eg. Matrix diagonalization, svd) but I need for ml to really understand things like angle between flats, tensor decomposition, etc