work ethic can 100% be trained/learned. it's just a habit, a different way of time management. it takes determination and sacrifice that some may be unwilling to give, but if they want it, it's there.
i think the biggest key is perseverance and persistence. as mentioned above, what separates the great from the good is the persistent, consistent work throughout the years and moods and pressures, etc. etc.
i do agree with your first point, lydian - there are lots of people with musical/technological talent, but not a lot who are willing to work hard (or long) enough to see that skill maximized (and in some cases, monetized).