When we consider the difference between virtuosity and Genius reasonable explanations are difficult and that is why we often read he was a gifted genius. I give a few examples in the realm of music.
Can a person be a genius at playing the piano? No since virtuosity is achievable by practice. Thalberg , Moscheles and Raff were all virtuoso pianists and wrote large quantities of music. Their music is rarely heard and largely forgotten today. Thalberg had astonishing technical skills and played many famous piano concertos to audiences of his day. These men also taught composition and counterpoint.
Works of genius have something in them that lasts. Genius cannot be taught but given the right material virtuosity can. A work of musical genius sticks in the general mind of mankind. It does not need to be technically difficult but it must move the soul in a memorable way. It is a lasting creation people want to hear again and again, and passes down the generations.