It seems not to be working. Keyswitches don’t sound. So, there is no way to map a keyswitch over a sounding patch limited to the same range.
For example, you may want to use C2 as a keyswitch for a hit. The percussion map will expect to find the hit on the C2 note. However,
If you map the sounding note over C2, that note is already taken by the keyswitch, and the VSL player will not play it.
If you map the hit to a different note, Dorico will not know how to play it, since a percussion map can’t differentiate between keyswitches and sounding note.
A percussion grid expects a percussion map. At least, if only using an expression map, there is no key switching in the target preset. Technique switching seems to be delegated to the percussion map exclusively.
Indeed, you cannot use KS or PC with a percussion map. As mentioned, it is quite easier to use an exp map for the gongs, but if you want to include some gongs in a percussion set and notate them on a one liner staff, then you’ll have to configure your vsl preset as an unpitched percussion and spread the sounds around the keyboard so no ks or pc are needed.
There’s still a possibility that combining exp and perc maps might work (I’m thinking using add-on switches), but I still didn’t try it and won’t have time for a while.
Québ
The result would still not be a percussion kit, but an ordinary preset with a particular programming. It will therefore not be able to react to a percussion map from Dorico.
Creating percussion kits in the VSL players doesn’t appear to be possible by the user. So, unless VSL decides to also supply the gongs as a percussion kit, I don’t see a way to do it on the user side.
As you know, a percussion kit makes keyswitches and individual sounds the same thing. Ordinary patches require a keyswitch to be selected, and a sounded note to actually play.