Re: PATCH: Arrowed accidentals for microtone notation

[Graham Breed]

2009/8/13 Joseph Wakeling <address@hidden>:

> A few comments on the proposed patches for microtonal arrow notation.
> I've already noted these on the Google Code Issue dedicated to this topic:
> http://code.google.com/p/lilypond/issues/detail?id=694

Oh, I didn't realize Google were covering this.  I've done some work
with Lilypond and microtonality.  Somebody said I should add something
to the snippets repository, but I've been lazy, so I haven't done
that.  There are examples in this bundle:

http://x31eq.com/magic/tripod-code.zip

> Briefly, the concern is this: that arrowed accidentals for quarter-tones
> (and indeed other microtonal intervals) introduce some new issues
> related to enharmonic equivalence.  The note a quarter-sharp above A
> natural can be notated either A-natural-arrowup or A-sharp-arrowdown,
> and it may be desirable to use both within the same piece of music.
> Similar issues apply to quarter-flats.

That can be done with a function to switch between different sets of
accidentals.  So \preferNaturals and \preferSharps, for example.
There may be ways of combining this with \once and \tweak as well.

> The problem with this approach was that it generated significant errors
> in transposition.  It could not deal with the case when transposition
> suggested a pitch alteration of, say, +4999/4000, to say nothing of the
> case when pitches would be transposed by quarter-tones.  (I have to say
> that the latter is a very tricky case anyway.)

If you insist on a certain spelling of quartertones, doesn't that
become a crap shoot anyway when you combine it with transpositions?
Like, if you have the quartertone below C, and you want it to be C
sharp up rather than C down, and then you transpose it up a semitone,
what would the correct spelling be?  How is the user supposed to
specify the correct spelling for both cases?

> Beyond the need for natural-up and natural-down as well as sharp-up and
> sharp-down, my main concern for Maximilian's patches is that they will
> also run into transposition issues of this kind.  Has this been tested for?

I believe there's  already a snippet for chromatic transposition.
That's probably the place to start for some of these issues.
Transposition certainly works for quartertones (and I've tested more
"interesting" situations) but you will get sharp-and-a-halfs coming
out.  But then normal transpositions might give you double sharps.  If
you don't want that I don't think it's a new issue with microtonality.


                 Graham