Date: 2021-10-08 22:10
In what I admit is only a two page search of dozens of posts here I can't seem to find an answer to this mostly academic question.
I call it "academic" because for the few times that we're called upon to trill from G#4 to A4, I imagine use of the second from top right hand side key on the upper joint, combined with embouchure changes, allows us to approximate how this trill would sound if we, say, ever had a right hand touch piece, that activated the A4 key normally actuated with our left pointer finger, at our disposal to effect this trill.
That said, has any clarinet maker ever, to anyone's knowledge, ever done such a thing?
Like I said, it's just a curiosity thing.
(P.S) I suppose in extreme cases, as a sitting player, we could put the instrument between our knees and bring our right pointer up to the A4 key, not unlike, how in far less extreme form, Mr. Williamson does here in the opening solo to Rhapsody in Blue!