You need to check what instruments you are using. Apparently (when I look at them in the Aria player) the Garritan brass instruments included with Finale do not have keyswitches.
In the add-on Garritan libraries (GPO, JABB) you need to be sure you have chosen the Notation versions of the instruments and the instruments with the KS (KeySwitch) suffix to have the benefit of the key switches.
You have found the KS Trumpet CAN play the Harmon sound, but (after extensive investigation) I have found that one can only activate the Straight Mute from expressions in the Finale file itself. Harmon and Cup Mute sounds do not work. (One can demonstrate this--if one's screen is large enough--by keeping the Aria screen open while one plays a piece that tries to activate the various mutes.)
I will file a support case about this.
UPDATE 8/11: Heard back from Kevin at MM, but we are still trying to figure out why what he can configure on his machine does not produce the same results on mine. Stay tuned.
Okay, Kevin from MM_Support got back to me with the following solution:
Open the test document that I sent
Choose MIDI/Audio > Human Playback > Human Playback Preferences...
Scroll down and expand the 'Garritan: Jazz, Big Band _Marching' listing (by clicking the black triangle to the left)
Click the "Brass: Cup Mute" line - this will highlight it
In the 'Filter:' dropdown box, change the entry to "(None)"
Repeat that step (#5) for the "Brass: Harmon Mute" and the "Brass: Bucket Mute" listings
Click 'Apply' then 'OK' to apply these changes
Try playback once again (It worked!)
Needless to say, I cannot attach Kevin's test doc, but this is what it looked like: you can create it yourself. Note that it is in the Handwritten Style (which gives you the proper expression library).
After failing to get any of the mutes to work with the exception of the "Mute" Expression provided, I found this thread. Here's what I have discovered two years later:
1. -- Using GPO or Personal Orchestra 5 1.a -- "Mute" works with n-Trumpet Plr1 KS, and the other "KS" listings for trumpet. 1.b -- none of the other mutes--cup, bucket, harmon--work 1.c -- this includes after going to Human Playback preferences and changing the "Filter" drop down to "None." The other mutes are only available under the Jazz listings.
2. -- Using Finale Default Bank > 011.Jazz > Trumpet KS 2.a -- ALL of the mutes work: cup, bucket, harmon, including the "Mute" in Expressions. 2.b -- I did not have to go to Human Playback preferences and change the "Filter" drop down to "None."
However, as with the jazz saxophones, the jazz trumpet has a pinched sound and a considerably lower volume. Working on a brass quintet, I use Personal Orchestra 5 instruments (n-) but tried the Jazz selection for Trumpet II. I set the GPO5 instruments with a dynamic of "mf," but had to make the jazz instrument "ff" (two levels higher) to match.
With a work for full symphonic winds, the solo alto and tenor saxophones are barely audible because my only choices are the jazz versions or the SmartMusic SoftSynth saxes. With that work, I have to set the mixer volume to full and all the rest to the middle of the slider for the saxophones to be balanced, or use "ff" against "mf."
Hope this helps.
BTW--In the GPO or Personal Orchestra 5, what do AG, SAM, and Overlay mean?
As you said, only the straight mute works with GPO. That's all that was ever available. I'm not sure if the straight mute was actually sampled or if the mute sound was created by programming. That's how it was intended to work.
The other mutes have always been available for the jazz instruments.
AG means aggressive. The AG overlay samples were made to be layered over other samples to give a more aggressive, biting sound. This is more practical to use in a DAW.
SAM is a reference to the SAM Brass. Project SAM is a sample developer. At some point in the past, they came up with new brass sounds. They made some sort of deal with Garritan, allowing Garritan to include the older SAM brass samples in GPO.
Oddly, n-Trumpet Plr1 KS and n-Trumpet Plr2 KS work with "Mute" and "Straight Mute" to turn on, but n-Trumpet Plr1 KS does not turn OFF with any of the Expressions. I've tried "senza sord." "Mute Off" "Mute Out" and "Open, but to no avail.
As above, I checked the Aria player, and everything is in place.
My only work around was to move the muted sections for n-Trumpet Plr1 KS into another Layer, and then assign n-Trumpet Plr3 KS or another with KS capabilities, and then return to Layer 1 for unmuted.
Again, this problem only occurs with n-Trumpet Plr1 KS.
I thought maybe a KS might have become stuck. Because mute ON and OFF worked for n-Trumpet Plr2 KS I tried that for trumpet 1, but to no avail.
I also created a new staff, copied all from trumpet 1 and pasted it into the new staff, and then used "Clear selected items..." to clear all of the Expressions. Again, it did not work for either n-Trumpet Plr1 KS or n-Trumpet Plr2 KS
Something must be stuck behind the scenes?
BTW--how does one apply the Keyswitch C2 (that you mentioned) with an Expression?