In the case of The Trumpet 3, there is, fortunately, only one key (C2) that has to be held down in order to trigger that “second layer” of articulations (which amounts to a further eleven keyswitches). So, in this instance (and, fortunately again), the actual playing range of The Trumpet allows enough space to accomodate these extra remote keys…
[EDIT] Apologies… you would indeed “run out of” available notes for remote keys on a five-octave keyboard, if you follow my recommendations “to the letter”, but read it anyways, then see the amendment at the end of this post… sorry again [/EDIT]
So (presuming that you are basically setting up the default “single” remote keys in your Expression Map to mimic The Trumpet’s own keyswitch assignment, i.e. C1 thru D2), what you need to do now is create a further eleven remote keys (e.g. D#2 thru C#3), where, for example, the remote key D#2 sends out two trigger notes (the “Output Mapping” section, at the top-right section of the Expression Map), e.g. C2 + C1 (for the “Chromatic” articulation), and the remote key E2 sends out C2 + C#1 (for the “Mixed” articulation).and so on up to remote key C#3 to trigger C2 + A#1 (for the “Half valve Fall” articulation).
[EDITING] with a single five-octave keyboard, there wouldn’t be enough “spare” notes for these extra remote keys, whereas, with an 88-note keyboard, you can at least adapt the map (move the remote keys down one octave, for example, or, alternatively, add these “extra” remote keys, starting at G#5 (i.e. just after the highest note of The Trumpet itself)
(Still thinking about a solution (if any ), if “stuck” with a five octave keyboard…[/EDIT][EDIT to the EDIT l)… see *** below[/EDIT]
But, admittedly, if there were more than one primary remote key (e.g. another set of articulations triggered by holding down a different key than C2), this would quickly become unmanageable anyways .
The nearest I have gotten so far (but I don’t think it is really a “playable” solution)… create a second Expression Map, with just the extra “dual” articulations on it, and use this on a second MIDI track, routed to the same The Trumpet Instrument. This does in fact work (so long as “Latch” is Off), but the problem of course is when switching between MIDI tracks.
My conclusion… Expression Maps aren’t really a practical solution for this kind of use. If this presents a problem inside the Score Editor (i.e. remote keys being seen as played notes), just Hide them, by declaring them outside visible range.