#4643 quarter tones in tablature

[Federico Bruni]

On a fretted instrument, like guitar (in standard tuning), there are no frets for quarter tones, but there are two cases where quarter tones in tablature are needed:

1. when the tuning contains a quarter tone
2. when you bend a string and produce a quarter tone

Harm wrote some code to workaround this limitation. This is currently the latest file:
https://lists.gnu.org/archive/html/lilypond-user/2015-10/msg00637.html

and later describes it:

Current 'determine-frets' from scm/translation-functions.scm checks
whether the calculated fret is an integer. If not, it throws a warning
and doesn't print it.
At first glance this makes sense, because there are no frets for
quarter-tones on a fretted instrument like guitar (in standad-tuning).
Though, ofcourse you can produce the quarter-tone pitch via bending,
which then is not represented in the tab.

Basically I changed it to check for (truncate fret) and removed the
according warning (letting the warning for negative frets in place).

This will result in frets like 5/2. Not that nice... So I added a
drawing-routine, 'my-format-tab-note-head' to use with
'TabNoteHead.before-line-breaking', printing 2½ in this case. (This
routine has some TODOs, I'm not really happy with it currently)

If we implement it in the source, we could
a)
simply change current code
b)
add an optional argument like 'quarter-tones?' to 'determine-frets'

[Thomas Morley]

quarter tones in tablature

issue 4643

micro-tones in TabStaff are now printable. Unless the chosen
string-tuning will allow it, this feature is disabled for
FretBoards.
- changing determine-frets (adding an optional argument) and
fret-number-tablature-format
- adding a regtest with quarter-tone-string-tuning
- documenting it in Documentation/notation/fretted-strings.itely
and Documentation/changes.tely

http://codereview.appspot.com/272320043

[Anonymous]

Passes make, make check and a full make doc

[Anonymous]

Patch on countdown for November 7th

[Anonymous]

Patch counted down - please push.

[Thomas Morley]

pushed to staging as:

commit 7f1b4934f96cfea964986c29d4048e6e794b9611
Author: Thomas Morley thomasmorley65@gmail.com
Date: Sun Nov 1 16:18:26 2015 +0100

quarter tones in tablature

issue 4643

micro-tones in TabStaff are now printable.  Unless the chosen
string-tuning will allow it, this feature is disabled for
FretBoards.
- changing determine-frets (adding an optional argument) and
  fret-number-tablature-format
- adding a regtest with quarter-tone-string-tuning
- documenting it in Documentation/notation/fretted-strings.itely
  and Documentation/changes.tely