The standard playback dictionary in Sibelius reads dynamic marking as velocity changes, and I realized yesterday that this meant that Sibelius was sending velocity changes along with my CC#1 messages. This means that ff passages also got hard attacks, which often sounded ok, but not always. Worse was that the pp passages got soft attacks, which was often not ok.
One way to solve this is to use live velocity levels and make changes there. This works fine, but I started wondering about methods that would allow me to bypass the linking of dynamic marks and velocity for GPO playback.
One possibility would be to create a custom GPO playback dictionary that did not recognize dynamic marks as velocity changes. This custom dictionary could delete the standard dynamic mark velocity changes. Instead a new set of marks could be created (something like vht for "very hard attack") that Sibelius would recognize as velocity changes and ~vht could be entered when a hard attack was wanted. This custom dictionary could be exported and then imported whenever GPO playback was wanted. (If regular Sibelius playback was wanted, a standard dictionary could be imported.)
At first I was frustrated by the difference between the function of velocity and CC#1, but then I realized that the ability to add crescendos and dim. to held notes with CC#1 was great, and would make no sense for instruments whose tone decays (like the piano). One drawback of a custom dictionary would be that if ff was no longer read as a velocity change, then for percussive instruments that rely on velocity changes for dynamic changes), a special velocity mark "vht" (or whatever) would need to be entered in addition to ff (needed for live performance).
Has anyone else thought about or tried going the direction of using a custom playback dictionary with Sibelius and GPO?
I use Sibelius 3 so I kind of know what you are getting at. Why don't you try technical help in your country from Sibelius to advise you on this or the chat page?
Try the chat page first - there seem to be a number of people who use GPO on it, and I'm sure you'll get some good advice from them.
I'm just not exactly a technical "wizard" with the area of Sibelius you are talking about.
I hope this advice helps.