I’m not a typographical expert by any means, but I find it fascinating. And it’s more than a mere curiosity for me—I often need to match existing styles from other typesetting programs (Finale, specifically).
The following mash-up is 33-point Minion Pro, screenshots taken from Dorico default, Finale, Adobe Acrobat, and then Dorico with 0.5 tracking.
I noticed right away that the Dorico default created a ligature between the T and the h. Then I noticed that every sample was a different length.
(I didn’t include it in the graphic, but MS Word produced a result almost identical to Dorico at 0.5.)
I don’t have a problem with the Dorico default. It’s quite nice. Except that I’m curious about the behavior of the ligature, and I want to be able to match font behavior. This example is negligible, but when it comes to hymnal lyric spacing (which can be quite tight), this margin of difference could be significant.
And I’m guessing from this little experiment that tracking is not a standard thing? That is, every software interprets font spacing differently? That seems like a strange practice to me.
Edit: I had referred to it as kerning, but I guess tracking is a more accurate term.