Finale uses MIDI Maps to associate MIDI note numbers with Sound Names (such as the Tambourine in the upper right pull-down of your Layout Designer image.

I no longer have access to F 2012, but here is an image from Finale v25. I hope you can find the equivalent route to access or create your own MIDI Map in 2012.

(I'm not saying I think this is the ideal way to handle this, but as Walter Cronkite used to say, "That's the way it is.")

Thank you very much for the information.

Accordingly, I have successfully made new customized percussion MIDI map.

I did not think the function should be accessed from MIDI/Audio.

For later reference,

 MIDI/Audio > Device Setup > Edit Percussion MIDI Maps.  (Finale 2012c)

Sincerely,

Jun Yamamoto

Jun Yamamoto,

Beware:

Percussion Layouts are saved inside the Finale document.

But not Percussion MIDI Maps.

Instead all Percussion MIDI Maps are stored in a special Finale program folder where the Percussion MIDI Maps are available to all the Finale documents on the computer.

This means that you, in the case of sending the Finale document to someone else, must send any custom Percussion MIDI Maps along with the document.

(Fonts, too, are not saved inside the Finale document. You must also send any non standard fonts along with the document)

I made Percussion MIDI Map for GPO5 Percussion Accessories.

For anyone who is interested in I put a link to the file. 

http://jun.la.coocan.jp/GPO5 Percussion Accessories.xml

Some of the sound does not have corresponding "sound name" in the list so that I put custom 1-13.

If I could change those "custom" instrument's name, it would be nice but it reasonably works with my score.

Thank you again.

Thank you for reminding me that Perc MIDI Maps are not saved with ".mus" file.

I noted it.

Sincerely,

Jun Yamamoto