It's Pi Day (3/14), so here's a brief thought with pie charts.
In my experience, most musicians start their careers with income from many different sources, all of which add up to hopefully be able to provide a living for them. As time goes on, I think it is often the goal for a musician to gradually take those many small pieces of pie and turn them into fewer and larger pieces of pie. This means they choose to pursue fewer, but more lucrative opportunities, and they often seek those which afford them the chance to use their strengths best. Sometimes explaining it this way encourages students and helps them understand the long game of making a career in music.
These charts are certainly influenced by my experiences and those of many others I know, but these are not reflective of any specific reality or musician.
Even this first chart simplifies things a bit, as the composing/arranging could include as many as 10-15 income sources. But you get the idea; the pie chart is more evenly spread and diverse.
But as a musician gets different opportunities that provide greater income, he/she may choose to let other things go and focus on what they enjoy most and what is most lucrative.
I would be curious to hear your thoughts and if there are musicians whose pie charts don't move in this same direction.
Happy Pi Day!