jem and james, my question was about whther it was a mere theory coonvention or whteher thhat trad. the playing was such that you could actually hear the distinction . ie a fiingering for Db that was different from a fingering for C# and WHICH resulted in a different sound.
They are slightly off from each other, yes.
If the player uses the wrong one for the scale he’s in, then you’ll hear it–at least if you’re used to listening to early music–as a note that’s “off” from the rest of the scale.
To someone used to equal temper, every note on the traverso is going to sound out of tune anyway. What’s a few cents here or there? 
–James
Talasiga, if you got hold of a traverso and a fingering chart for it and played through the alternate enharmonic fingerings unaccompanied, you would hear the pitch differences readily enough, and they would be clear to see on a tuner. You can achieve some of the same effects on a C19th 8-key by similar means, though by then it was less a part of regular performance practice and sensibility. For both performers of the era and for todays HIP specialists, using these techniques was/is normal. How perceptible they are to a listener depends somewhat on the listener! However, I think most listeners, even the very “uneducated” would hear the difference between performances on period instruments and modern ones, not just in simple tone colour of the actual instruments but in a subjective, atmospheric way to do with the “feel” of the music - and that is where the temperament issues kick in. You don’t have to have studied it to hear/feel the difference, but without necessarily being able to analyse it, let alone spot that e.g. a Db is being played rather than a C#. A highly educated ear or one naturally gifted with precise pitch awareness would be able to be more analytical of what is going on, for sure: someone cursed with so-called “perfect pitch” and inculcated with 12TET at A=440 would just hear it all as “out of tune” (their loss!). To most unprejudiced listeners not suffering that particular handicap, well done HIP soon starts to sound more sympathetic to the music and more subtly interpretative of it than modern instrument “straight” playing of it, once their ear acclimatises to the different aesthetic.
I don’t find that.
I loved your traverso interpretation
of ITM.
I have a hunch that you may find
this topic from a totally different site
interesting reading …