In “Halion Sonic SE2” the keyboard is not correctly shown.
The middle key C3 (index=60, Freq=261,63 Hz) must be called C4.
The marking of the keys must be shifted around an octave to the left. The 1st key is A-1, however, must be A0.
In Play-mode the keyboards are correctly shown.
I hadn’t realized the different identifications within Dorico and agree this is problematic. The underlying problem is that terminology identifying octaves is not standardized worldwide and Yamaha, which owns Steinberg, including Dorico, normally identifies octaves differently than many other sources.
Many programmers use the term in the software for piano from A0. That would fit to the play mode in Dorico.
Yes, it is not so important which index the octaves have. Like you said: “terminology identifying octaves is not standardized”.
I wanted to point out here to the fact that in Dorico the user’s interface should be uniform/consistent.
“Halion Sonic” and “Play-Mode” should have the same name for octaves.
Thank you Paul, I have not found before that issue.
I find that C4 is a right choice.
I know that you can not easily adjust the other programs/libraries (compatibility with previous versions, etc.).
Importantly the fact that they know it, and maybe one catches up sometime.
A small note in the user guide would not be bad.
As comedian Steve Martin once said about foreign languages, "Those French have a different word for everything!
(Not to pick on the French: Steve Martin could have chosen any language for his routine.)
I’m sure we can all adapt to some choosing C4 and some choosing C3 for middle C, especially if there is a note somewhere in the documentation as you have suggested.
I’m still confused by this C4/C3 discussion. I suppose this comes from MIDI?
Here in Austria we refer to the c on the first ledger line unter a treble clef staff as “c1”, the c one octave higher would be “c2” and so on. The c one octave lower (in the middle of a bass cleff staff) would then be just “c”, one octave lower would be “C”. That’s the way I learned it in music theory.
So when I read here C3 I think of a c two ledger lines above a treble line staff, while you talk about the note I’d call “c1”… Quite puzzeling 
I think it was said already about this topic… 
Yes, mine I also, it gives an amount from names for C=midi[60].
It isn’t about that, it should say C3 or C4, it could mean too X.
Like I said:“Halion Sonic” and “Play-Mode” should have the same names for octaves (uniform/consistent/unequivocal).
Because the team cannot adapt so simply, for compatibility reasons for other programs/libraries, we must come with it so rightly. 