Re: [Patch:] Negative fret numbers cause a warning (issue 1035)

[Marc Hohl]

Am 22.12.2010 22:02, schrieb Carl Sorensen:
> On 12/22/10 4:16 AM, "Marc Hohl"<address@hidden>  wrote:
>
> > Am 22.12.2010 09:48, schrieb Carl Sorensen:
> > > On 12/22/10 1:30 AM, "Marc Hohl"<address@hidden>   wrote:
> > >
> > > > Hello all,
> > > >
> > > > attached is a small patch to handle Issue 1035.
> > > >
> > > > Instead of giving an error, it raises a warning when negative frets
> > > > are calculated in tablature staves or in fret diagrams.
> > > Marc,
> > >
> > > If instead of being inside set-fret, this check took place in the form of a
> > > (string-qualifies string (note-pitch note)) check at line 455, we could
> > > issue the warning and then try to find a valid fretboard/tablature that
> > > would handle the pitch, assuming the string number was incorrect.  That way,
> > > we'd still have the note in play, and the string would be available for
> > > other notes.
> > >
> > > I think that's a more robust way to handle it than setting the negative fret
> > > number.
> > Hmmm - I wrote some tunes with a capo placed at the third fret but covering
> > only strings one upto five, so the sixth string still sounds with an open e.
> >
> > I didn't wrote it down, but if I ever do so, I wonder whether the open e
> > would be written as fret number "-3" in tablature relative to the capo
> > position.
> Hmm -- I wouldn't write things down relative to a partial capo.  I think the
> meaning of a 1 on the e string is unclear if you do that.  Does it mean the
> first fret or the fourth fret?
>
> If I were writing music with a partial capo, I'd probably write everything
> relative to the nut.  Or perhaps I'd change the string tunings to reflect
> the presence of the capo and indicate somewhere on the score that frets were
> relative to the capo on the capo'ed strings and relative to the nut on the
> non-capo'ed strings.
Well, this seems to be a rather philosophical question, but assume
I have a partial capo on strings 1-5 and I want to play a Bflat major chord
in G shape.

A pattern like

Capo III (1-5)

-3-
-3-
-0-
-0-
-2-
-3-

seems to me more readable/understandable than

Capo III (1-5)

-3-
-3-
-0-
-0-
-2-
-6-

which at first glance looks like only Allan Holdsworth would be able to 
play ;-)

> > Despite this rather artificial example, I don't know whether we should make
> > lilypond more "intelligent". Sometimes I did make some octavation errors and
> > spotted the erroneous negative numbers after printing the scores and handing
> > out the copies to my students (therefore way too late ;-) - the string
> > number
> > was right indeed, but I forgot a "'".
> OK, so in this case, you didn't see the negative numbers because they were
> part of the tablature.  Your tablature ended up clearly wrong -- the
> tablature literally couldn't be played.
Yes, but in this case the normal staff is wrong, too, so I have to rework
it in any case.
> The warning here shows that there is a mistake.  The fact that we were
> missing a warning is a bug, and we really need to add a warning.
Yes, of course.
> [...]
> I think we agree on the fact that a warning should be printed.  The only
> remaining issue is what to do with the note having the negative fret number.
> I see three possible choices (and all are achievable with code).
>
> A) Go ahead and include the negative fret number in the tablature and the
> fretboard.  In terms of fretboards, this might be preferred behavior,
> because the fretboard will be ugly and should be easily visible.  In terms
> of tablature, I think this is the worst behavior, because it creates an
> impossible note to play and it's not clearly visible.
You're right, but I have to take the warning into account (as with
open strings, unterminated ties and more). If I know that there is something
wrong with my tablature and I have to search for a negative fret number,
I'll find it very soon.
> B) Leave the note out of the fretboard and the tablature.  This makes no
> assumption about the relative importance of the pitch vs. the string.  Since
> we don't know where the error is, we just drop the note.  This has the
> advantage that the music is playable, but the major disadvantage (IMO) that
> there is no evidence in the music that something isn't right (unless you
> have both Staff notation and TabStaff notation, where you can see there is
> a missing pitch).
>
> C) Try to find a string that will allow the note to be played.  This assumes
> that the pitch is right, and then tries to make the tablature match the
> pitch.  In this case, the TabStaff will always reflect the notes on the
> Staff if possible.
>
> Your preference, as reflected in the patch, is to do A.
>
> My preference is to do C, because I think that the TabStaff should always
> match the Staff if possible.  That's the behavior I chose (and you agreed
> with my reasoning) when dealing with an improperly labeled open string.
C sounds reasonable, but it will cause lilypond not to allow for
negative frets without hacking the fret number printing callback,
and while I don't know whether it is standard, I think *I* will probably
need them in the future. So for me, the warning is ok, saying
"hey, you are specifying negative fret numbers, I hope you know what
you do" - and if it is a "normal" piece of music, I will check the resulting
score for these errors, as I would do for things like a ~ b .

But I am open for discussions on this, of course ...

> [...]
>
> Thanks for all your work on LilyPond, and for your work on this issue in
> particular.
Well, I still think I should spend more time on lilypond, and for 2011,
I'll give it another try, but that's another issue...

Thanks for your kind words!

Regards,

Marc