Re: Microtonal accidentals

[Keith OHara]

Joseph Rushton Wakeling <joseph.wakeling <at> webdrake.net> writes:

> On 07/11/13 07:26, Keith OHara wrote:
> > The arrow notation also gives two options for the half-flat: natural-down-
> > arrow and flat-up-arrow.  If someone uses both options for the half-flat in
> > the same piece, LilyPond can keep track of the choice by using a tuning
> > system that has them at slightly different pitches.
> 
> I've discussed at length why that is problematic.

The use of two alterations, natural-up and sharp-down, for the same pitch
where the note-head is on the same staff-position is problematic to read.
I would hope that composers choose one glyph and use it consistently
within a piece.  

If you mean that, when natural-up is distinguished from sharp-down,
representing the alterations as different pitches causes complications
in transposition, that is because the potential results of transposition
are actually complicated.  It is not obvious whether sharp can be used
to represent natural-up-up, but we can tell LilyPond by putting the 
sharp glyph in the table at the pitch of natural-up-up.

If LilyPond represented alterations with count of sharps and a separate
count of arrows, she would still need to know the rules for when to convert
two up-arrows into a sharp.  In Johnston notation, she should never do so.
The arrow and sharp are usually composed into one glyph by a human, so
LilyPond would also need a method to convert the arrow-count, sharp-count,
etc., into an index into the font that contains the glyphs.

This might be problematic, but seems to be problems better resolved
by the human who understands the music, than by the computer program.

> It also rapidly becomes 
> unworkable once you start dealing with intervals finer than quarter-tones, 
> simply because of the number of cases you have to deal with.

This is what I looked into.  It seems to me that systems with finer
intervals are necessarily more frugal and more systematic with the symbols
they use to denote the alterations.  I found no other cases where two
symbols are conventionally used to represent the same alteration.