Re: tie over clef change

[Hans Åberg]

> On 26 Sep 2020, at 19:56, Werner LEMBERG <wl@gnu.org> wrote:
> 
>>>> The notes d♯ to e♭ have different pitches in the staff notation
>>>> system, which cannot express E12 enharmonic equivalents, so this
>>>> is slur. So it should be a slur that looks like slur.
> 
> I disagree.  For all practical purposes in standard classical music,
> enharmonic equivalents *do* sound the same.  What you are referring to
> IMHO is a special case that might be controlled by a flag.

They do not, and the string section, that primarily stands for the pitch 
reference, trains to slide the pitch appropriately:

In the video below, time 10:43, Brett mentions that the E (on the D string) 
against the open G, the sixth, is a bit lower than against the open A; the pure 
fourth. This is the syntonic comma 81/80, the difference between the Just 
Intonation major third 5/4, and the higher Pythagorean major third.
  https://www.youtube.com/watch?v=dW9t7Nrin_c&t=643

This is for adjusting towards Just Intonation, but it is necessary for 
enharmonic equivalents too, as the Pythagorean comma is the microtonal amount 
they use in Turkish music. A melody line will not sound right if not adjusted.

>> I can think of special cases: Perhaps the tie and the slur are
>> rendered slightly differently, say of different thickness, so in
>> Werner's example it should be a tie in style.  Somebody might want
>> to indicate an E12 enharmonic equivalence, as in your example, even
>> though it is not so in the staff notation system, and then it should
>> be a tie in style.
> 
> As mentioned above: This might be controlled by a flag.  Or maybe a
> special “E12_tie_slur” engraver can handle this.

You probably think of how to handle it internally, because syntactically one 
might just write a tie between enharmonic equivalents.