Re: TimeSignature with note in denominator

[David Kastrup]

Carl Sorensen <c_sorensen@byu.edu> writes:

> On 11/13/21, 4:05 PM, "David Kastrup" <dak@gnu.org> wrote:
>
>     Kieren MacMillan <kieren@kierenmacmillan.info> writes:
>     
>     > Hi David,
>     >
>     >> It doesn't answer the question.
>     >
>     > Did my explicit answer in the other email (i.e., “one
>     > quintuplet-sixteenth-note”) not suffice?
>     
>     No.  You propose replacing (cons 3 4) as a time signature designation
>     with (cons 3 (ly:make-duration 2)).  You have failed to give any
>     indication of what you want to see (cons 8 20) replaced with.
>
> What if the time signature description were (cons 3 '(2 0 1/1)) or
> '((rep 3) (dur_param (2 0 1/1))?
>     
>     LilyPond does not have something like a 1/20th duration.  Regarding
>     durations, what occurs inside of \tuplet 5/4 and \tuplet 10/8 is
>     completely indistinguishable: "tupletism" is not a part of durations.
>     
>     So I repeat: what duration in LilyPond do you want to use to represent
>     the denominator in 8/20 ?  1/20th here is neither a 5-tuplet nor a
>     10-tuplet: it represents a fraction of a whole note, not a particular of
>     several possible note values.
>     
>     It will likely end up as (ly:make-duration 4 0 4/5) but that has no
>     unique printed representation different from (ly:make-duration 4), and
>     (ly:make-duration 4 0 4/5) and (ly:make-duration 4 0 8/10) are
>     absolutely indistinguishable.
>
> The alist I proposed above would be able to distinguish between 4/5
> and 8/10.

No it wouldn't.  Scheme does not distinguish 4/5 and 8/10 .  And neither
does the composer using a time signature of 8/20 whether this suits your
theories about what time signatures "really" are or not.  8/20 conveys
more information than a proper fraction (which would be 2/5) but less
than 8 times a particular note duration expressed as a specific kind of
tuplet.  It's 8 times 1/20 without detailing how that 1/20 is
constituted.

> I don't know if it's a good idea, but it is an idea.

-- 
David Kastrup