You do not need classes for that. Kerning is always between two distinct glyphs.
So you can add a kerning pair for TA (lets say with a value of -100) and for PA (with a value of -75).
Kerning classes on the other hand are interesting for grouping similar glyphs together and so that you not need to kern them all over and over again. This is done for all accented letters. So you put all "A"s in on class (like A, Aacute, Adieresis, Agrave …). Then, If you kern TA, TÄ will have the same kerning.
Georg
Could you describe the process for creating kerning classes? I thought I had it figured out, but it seems to create individual kerning pairs instead.
In the main window, near the bottom left there’s an area for entering the left and right kerning classes. If I set A and accented instances of A to both left and right A class, are there any other steps I have to take to create that class?
in an Edit tab, you type an A and move your cursor to the left side of it.
in the grey Info panel beneath the A, you see left and right kerning groups (‘G:…’)
enter an A into both groups, like this:
Do the same thing for Adieresis, Aacute, Agrave and so on. This way, you add these glyphs to the left/right kerning group of A.
Now, type ‘TAP TÄP TÁP’, move your cursor between T and A, and kern by hitting ctrl-opt-left/right arrow. Make sure the lock symbols, which appear next to the kerning group names, are locked. That means you’re editing the group kerning. You should see all combinations TA, TÄ, TÁ and so on kerned the same way.