What’s common between software engineers and musicians?

This came out of a conversation I had recently, with a software engineer whose wife is a musician.

1. They both express their ideas via instruments that have hardly changed for long time, although frequently tweaked.
2. They both express the creativity under a strict set of rules that are mathematical.
3. The forms of the expression are of convention, not rules.
4. Individuals who practice the art are hardly rich. Institutions that hire many of them tend to reap most of the wealth out of their creativity.
5. Both like to spread their work freely. Both struggled to find a way to monetize.

Anything else?