Select by Pattern while deselecting non-matches?

Hi
I'm running the latest version 12.27 on Windows 10.
If I highlite a file in a directory, for example. info.txt and then do a select by pattern '*.mp3",
the 'info.txt' file will still be selected. I would think only the '.mp3' files would be selected and the
.txt file would be de-selected
Thanks
Al

If you want it to work that way, edit the menu item and change the command from
Select
to
Select DESELECTNOMATCH

OK, how do i do that?

Settings > Customize Toolbars, then open the menu and double-click the thing you want to edit.