Re: Contemporary music required feature #1: chromatic transposition

[Joseph Wakeling]

Hans Aberg wrote:
> I think LilyPond, once it has found the correct scale degree, computes
> the interval offset. As there is none for this particular offset, it
> typesets nothing. It should report at least a warning, though. The value
> stored inside should though be correct.

Yes, I think this is exactly what it does -- and it does report a warning.

> So I think you need to add a choice of glyph. LilyPond is too primitive
> to treat # and b and other accidentals as operators acting on all
> intervals.

Well, the point is that a glyph for 5/4 sharp is nonsensical.  A
contemporary music player would be pissed off enough at seeing a
double-sharp in non-tonal music, to say nothing of a 5/4-sharp symbol.

>>> In this case, staff position only changes if enharmonic equivalents are
>>> applied. This is how it should be.
>>
>> That's why I stress I want this as an _option_ for transposition, not
>> default functionality.
> 
> I think one needs to think through carefully how one wants to enharmonic
> equivalences be applied. It may vary with context. On most instruments,
> it can be used to simplify key signatures. On a harp, it may have to be
> applied note-by-note, as double sharps and flats are not available. If
> the tuning is other than E12, it implies a small slip in pitch.

Yes, that's a good point I hadn't considered.  The naturalizeMusic
function serves the harp's needs well, where 3/4-sharps and flats are
not possible.  (Was that the motivation for this function?)

So basically we are talking about a 'modulo effect', i.e. to constrain
every accidental to 'modulo a' where a is an alteration: for the harp,
to modulo 1/2, for standard chromatic transposition, to modulo 1.

That might actually be the best way of looking at it -- relative to a
maximum acceptable size of alteration.  (Tricky would be
less-than-or-equal-to versus less-than.)

Best wishes,

    -- Joe