I am trying to understand how drum substitution works. As an example, a line from the a_pgmusic.ds file is:

JAZSIMP.sty=JazzBrushes/4,Jazz/4

What is the relationship between each of these entries and the RD Settings 'Favor Brushes/Sticks' and 'Favor Artists'?

My theory is that the first entry (JazzBrushes) is the default brush kit and (Jazz) the default sticks kit. If the Favor Artist is selected, the '#1' is appended to these.

Am I correct?

Thanks,
R

In the example above, JazzBrushes would be used (because it is first in the list), unless you don't have it, in which case Jazz would be used.

That assumes that you haven't made a preference under "Favor Brushes/Sticks"
If you have....

If "Favor Brushes" is selected, then "Jazz Brushes" would get used, as only styles with "Brush" in the name would get included.
If "Favor Sticks" is selected, then "Jazz" would get used, because styles with the name "Brush" would get excluded.