Carl Sorensen <[email protected]> writes:
> On 11/15/21, 10:21 AM, "lilypond-devel on behalf of Flaming Hakama by
> Elaine" <[email protected] on
> behalf of [email protected]> wrote:
>
>
> According to the semantics quoted several times, the denominator describes
> the length/duration of the unit, the numerator describes how many units
> are
> in the measure.
>
> There is some space for confusion in the LilyPond world. Moments represent a
> musical moment, an instant in time. But a moment is also used to represent a
> time interval between the current moment and the zero moment (such as the
> beginning of a measure). So a moment also can be used to represent an
> interval, as is applied in the time signature. I should have been more
> sensitive to this, because I created the BaseMoment property to be used in
> autobeaming; this property represents and interval starting at 0 and ending
> at the moment BaseMoment.
>
> In terms of semantics, numerals and note representation operate exactly
> the
> same. There is a 1-1 mapping between numbers interpreted as fractions of
> a whole note, and the graphical symbols used to represent those
> durations/lengths.
That is simply untrue.
\tuplet 2/3 { 4 } and 4. are different graphical symbols representing
exactly the same length. Similarly \tuplet 3/2 ... and \tuplet 6/4
... represent the exactly the same length but have different graphical
representations, note durations and musical semantics.
Claiming that there is a 1-1 mapping and that one can exchange on for
the other in the internals without consequences is just not going to
help.
And there is a huge tendency here to conflate that the existence of an
n->1 mapping for durations/graphics to a moment length with the
existence of a 1-1 mapping and to build lots of strawmen based on
claiming I deny the existence of the n->1 mapping and "proving" in that
manner that I don't know what I am talking about.
> Now, music expressions also have a length, even if they don't have a
> lilypond duration. And it is possible to get the length of a music
> expression and return it as a Moment using ly:music-length. So if it
> were possible to have the parser (or a music function) take two
> arguments for a time signature, with the first being an integer and
> the second being a music expression, it would be relatively
> straightforward to convert this into a reasonable time signature.
Where "convert this into a reasonable time signature" would imply the
ability to convert this into the two separate components, a functional
and a visual one. At the current point of time, something like
2/4. (for what is commonly referred to as 6/8 in standard notation) has
no natural conversion to the functional components
numerator/denominator. One could do this "more naturally" by allowing
the "denominator" to be a rational number instead of just an integer.
The _visual_ component still needs a separate expression that probably
sticks best with being actual music once one puts out note images. That
would allow for example a meter of 4 times \tuplet 3/2 { 4 8 } for some
weird swing time indication, or 3 times { 8 8 8 } for a different
representation of 9/8 meter.
With regard to meters, obviously there are also numeric variations like
writing 3+2 in the numerator. The amount of visual possibilities is
large enough that forcing visual and functional components to be
interchangeable seems like a bad idea.
--
David Kastrup
