How shuffle mode works

OK, after a running in shuffle mode for a while I have guesses on how
it works.

First it picks a CD

Then it checks to see if that CD (or its tracks) has

any of the keywords specified.

Then it picks a track.

If it doesn't find a track based on keywords then it will pick the track

based on the slider preferences.

My supporting data is:

A CD which only has one track that meets the keyword criteria will get played significantly more often than the tracks on a CD that has all its tracks meeting the criteria.

The slider preferences "effect" is more noticeable when there are no
keywords selected. In fact it doesn't seem make any difference when
there are keywords in play.