Peter, what is the meaning of numeric parameter to RANDOM and PLAYS? I didn't quite understand from that mail Doug quoted.

They are the weightings given to each factor in determining the track's "soonness factor".

Suppose the shuffle we're doing is "PLAYS=32000,RANDOM=1". Then, for each track, the number of plays is multiplied by 32000 and added to a random number (1-32000) is multiplied by 1. The resulting number is the "soonness factor" for that track. Tracks with lower soonnesses play sooner.

Are the mode label (shuffle0) and menu name (Favourites) arbitrary?

The labels (shuffle0, shuffle1) are not arbitrary and must be consecutive and starting at 0. The menu name ("Favourites") is arbitrary.

How does one specify other tags, if at all (like in searches?) (for example, 'play randomly, but prefer tunes Wendy-tagged as not being suitable for mother-in-law's ears)?

You can use TIME, PLAYS and RANDOM as described in the Big Yellow Email, plus any numeric database tag -- of which there aren't many; YEAR is about the only useful one. (A future release might add MTIME, so you could shuffle favouring tracks recently added to your player.)

(A far-future release might include the original intention of being able to add custom numeric tags in emplode/emptool. So you could assign a numeric "cheese factor" to Britney Spears, Steps etc. and then shuffle favouring cheesiness -- or suitability for fast driving, or for dancing on the back seats, or whatever.)

I guess one cannot combine parameters (e.g. maximize(plays-2*skips))...

No, that's exactly what one can do. One is only prevented from specifying that particular shuffle, by the fact that keeping count of skips isn't yet implemented.

Peter