Re: Diatonic notation system

[Graham Breed]

2008/12/7 Hans Aberg <address@hidden>:

> That is not the problem , but that whole tone is not the double of the half
> tone. M = 9, m = 4, so that there are 5*M+2*m = 53 tonesteps or commas in an
> octave.

How is that a problem?

> The same problem is in meantone tunings, in E31, M = 5, m = 3, so that M/m =
> 5/3.

I still don't see a problem.

> When I looked at it, it computes accidentals as an offset from the
> whole-tones, which are six to the octave. That forces E12, and for
> intermediate pitches a multiple of 12.

Oh, this looks like a problem.  I don't see a way of defining the
nominals after all.  The documentation for ly:make-pitch talks about
"pitch C" and "pitch B" without saying what they're supposed to be
tuned to.  So you need to define a Scheme function that takes a
rational instead of an integer for the number of scale steps and sets
"alter" accordingly.  And probably a Scheme function to set up 7
definitions of each accidental to take account of the 7 different
nominals they could be applied to.  There's support for ancient
notation so surely it must be easier than this to define historical
tunings...?

Yes, the intermediate pitches are specified as fractions of a whole
tone.  How else do you suggest that be done?  You can write a function
that converts from your chosen units into fractions of a whole tone
with whatever precision you choose.

>> It's all Scheme code.
>
> And particular part was not alterable by Scheme code.

The whole file's Scheme code.

>> As Sagittal isn't working we are a bit short of sharp symbols.  There
>> are some arrowed accidentals on the way, though.
>
> This would be the long haul.

I made good progress during the summer.  It'll hopefully work as soon
as someone looks at setting the relevant tables in the Sagittal font.
A python function in Font Forge is how I'm told it's done.

> A more immediate concern would be fixing Arab music. The guy who didi it
> fixed it at E24, because they use such symbols, but everyone agrees that the
> intermediate pitch is not an exact quarter-tone.

So change the init file.

> Now that fixation is not only a problem for MIDI files, but may cause
> transposition problems, as a half-flat may be erroneously altered to a
> half-sharp on the semi-tone below.

Could it?  Define the "half-flat" as a bit less than half a semitone, then.


                             Graham