Re: [GLISS] non-timed or non-musical events "z" "y"

[David Kastrup]

Joseph Rushton Wakeling <address@hidden> writes:

> Step back for a second and consider the variants you might want in a tempo 
> change:
>
>   (1) specified beat unit has a particular number of bpm.  Your beat unit
>       may not be limited to a "typical" unit like a quarter- or eighth-note,
>       but might be a 5th, 6th, 10th or 12th note (i.e. quintuplet or triplet
>       quarter or eighth), or it might be a combination of note values (e.g.
>       two note values tied together, say 8 ~ 8. or 4 ~ 10).
>
>   (2) Beat unit unchanged, but bpm changed to a multiple of previous value
>       (e.g. tempo doppio, etc.).
>
>   (3) New beat unit tempo equal to a multiple of a beat unit in previous 
> music.
>       Simple case here is e.g. half-note tempo = previous quarter-note tempo,
>       i.e. 4 = 2 or 2 = 4 depending on what way you want to write it), but it
>       could also involve much more complicated beat units as already described
>       in (1); e.g. 8 ~ 8. = 4, or 10 = 12, or, ...

With the separately discussed "isolated durations are pitch-less
NoteEvent in noteentry", you could use arguments like
{ 8 ~ 8. } = { 4 }
and such music arguments would get passed through a \score markup using
a specific TempoStaff without stafflines and with nice dimensions, also
allowing for specs like
\tempo \times 2/3 { 4 8 } = 64

Basically, one would have to vary the typesetting depending on whether
the right side contains a number or music, assuming music on the left
side, and measuring out the lengths of the music.

> Ideally the Lilypond tempo syntax would allow for all of the above
> kinds of tempo change.  Does it currently?  And is it possible to
> imagine a practical syntax that allows for this?

The equals sign might come into play at some later point of time, and
tempo _ranges_ are not really something I see fitting well.

-- 
David Kastrup