After a lot more experimentation, I believe I understand how the Sync Region tool operates. Coming from a DAW with very different behavior for selecting and copying CC data (simpler yet powerful), I was confused by exactly what was meant by “region“ in this context.
When, say, you enter some pencilled data into 1 1/2 bars of Dorico’s dynamics track, a “region” is created containing that pencilled data. The boundaries of that region are the beginning and end of the pencilled data. In this case, the region equals 1 1/2 bars of music on an instrument track.
Then, with the sync region tool, you tap (or lasso) that region and it syncs across the multiple instruments visible in the Key Editor.
But suppose you want to sync only the middle half of that region… you can’t, as far as I can tell. The only way to sync the data for half a region is to exit multiple instrument mode and then select, copy, and paste the CC data into each track by hand. This can be time-consuming and error-prone.
I’d like to suggest a much simpler user experience, one that extends the functionality of the Sync Region tool while permitting the same functionality.*
Select an arbitrary area in a CC or velocity track of the primary instrument. Press Sync Region and that arbitrary area’s data is sync’d across the multiple instruments selected. If the chosen area includes both program-generated and user-customized CC data, the Sync Region function should take into account the values generated by Dorico’s built-in dynamics algorithms as well as the user-customized data.
That, in fact, was what I was trying to do. There was an extended area of my score. that contained a lot of CC data. All I needed was to sync the beginning of that area across all four instruments in a string quartet. It proved impossible.
If my suggestion is implemented, the current behavior of the Sync Region command could be replicated simply by selecting the first point of an area containing custom CC data exclusively and the last, and then enabling Sync Region.
Anyway, I hope this explanation will be useful to others who are trying to understand how Sync Region works. Naturally, if I’ve misunderstood or made any mistakes, I’d be very grateful if someone would correct me.
*Whether my suggestion is easy to program is another story. I’m not a programmer and don’t know what would be involved. I know that Dorico is not intended to be a full-fledged DAW, but from a UX perspective, this doesn’t seem to me to be too much to ask.