The default Garritan Sounds which ship with Finale 26 do not support “unison” groups of reduced player configurations such as a2, a3, a4 etc., but if you are a NotePerformer user, you are in luck.
NotePerformer 3 installs a Finalescript folder containing a number of Finalescripts labeled “UNISONS – Playback to Expression”. There are scripts for a2, a3, a4, a5, a6, a7, a8, and “solo/default”, which will either restore playback to one player for a solo instrument, or the default ensemble.
These Finalescripts work by adding appropriate MIDI controllers to selected “a2”, “a3” text, thereby defining their playback characteristics.
You can use the scripts to add this MIDI Controller data each time, but it’s also easy to define these in your Finale score template so you don’t have to run the scripts each time to get this enhanced playback in NotePerformer. Here’s how…
In your score template, select the Expression tool, then double click in a staff to open the Expression dialog.
Navigate to the Technique Text category, and create or select “a2”.
To Edit the Expression in the Expression Designer, click on the Playback Tab, and choose “Controller” in the “Type” Popup. Enter “104” in the entry field, and then in the Effect: Set to Value, type a value of 2 (for a2).

Repeat the process to define playback for a3, a4 etc. For single instruments, you can define “Solo” with Controller 104, set to value 0. This same controller value can be used for “tutti” text for ensemble instruments such as Strings. This is a reset to the instrument definition default.
Remember, if you are using an ensemble sound such as “Violins”, applying Solo text defined with controller 104 set to 0 will not work here; controller zero resets NotePerformer to the Default sound for that instrument. To create a solo Violin passage in an ensemble violin staff, use an instrument change.
Here are the MIDI Controller settings for Playback in Finale:
Solo / Default (tutti) Controller 104, Set to Value 0
(this resets to the default single or ensemble sound)
a2 Controller 104, Set to Value 2
a3 Controller 104, Set to Value 3
a4 Controller 104, Set to Value 4
a5 Controller 104, Set to Value 5
a6 Controller 104, Set to Value 6
a7 Controller 104, Set to Value 7
a8 Controller 104, Set to Value 8
Now, save your template so you can use your new playback settings for future projects.
You can also save a group of Text Expression definitions with playback as a Library for easy recall.
In a New Document Without Libraries (so you only save the small group of expressions for this purpose), create the above set of “unison” expressions with their playback definitions, then Save them as a library (File menu, Save Library…)

These Expressions will now be available to you with the proper playback definitions when you Load Library…
For your convenience, you can download a set of these unison expressions for NotePerformer with their definitions already assigned here.
That’s all there is to it!
~robert