Re: polyphony and TabStaff: don’t put two voices on the same string (Malte Meyn)

[Christopher Heckman]

On Sat, Oct 19, 2019 at 9:00 AM <address@hidden> wrote:
>
> Date: Sat, 19 Oct 2019 10:06:10 +0200
> From: Malte Meyn <address@hidden>
> To: bug-lilypond <address@hidden>
> Subject: polyphony and TabStaff: don’t put two voices on the same
>         string
> Message-ID: <address@hidden>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
> Hi list,
>
> this was reported at the LilyPond facebook group. When having “real”
> polyphony with multiple Voice contexts, the notes are put on the strings
> independently which can lead to several voices with different frets on
> the same string.
>
> The first three “chords” on the TabStaff should look the same (1st
> string 3rd fret, 2nd string 5th fret). I’m not sure about the correct
> handling of unisons (second three “chords”) in polyphony because I don’t
> play guitar ;)
>
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> \version "2.21.0"
>
> music = \relative {
>    <g' e>2
>    << g e >>
>    << \tweak TabNoteHead.extra-offset #'(0.3 . 0.3) g \\ e >>
>    <e e>
>    << e e >>
>    << \tweak TabNoteHead.extra-offset #'(0.3 . 0.3) e \\ e >>
> }
>
> <<
>    \new Staff { \clef "treble_8" \music }
>    \new TabStaff \music
>  >>
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>
> I tweaked the extra-offsets so that you can see that LilyPond just
> prints two TabNoteHeads in the exact same space.
>
> Cheers,
> Malte

Even worse, Lilypond can slide from one note to a note on another
string, with something like c \\glissando c'. (The octaves might need
adjusting.)

A few years ago, I worked on an improved tablature algorithm, but
could never get github (or something like it) to work so that other
people could test it out. It would have fixed bugs like this, as well
as being able to tab chords like <c d e> (c on E string, d an open D
string, and e on the A string) that Lilypond can't currently handle.

--- Christopher Carl Heckman