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

[Joseph Rushton Wakeling]

On 23/09/12 00:07, Graham Percival wrote:
> I have no problem with splitting \tempo into a \tempo_bpm and
> \tempoMark command.  Or perhaps it would be better to just use
> \mark, and add markup functions which mimic the "text" parts of
> the existing \tempo command (if they don't already exist, which
> they probably do).

That seems potentially quite "ouch" -- too much chance of the user tweaking the 
visual mark but not the actual bpm, or vice versa.

OK, perhaps you could make it so any metronome mark in the \tempoMark is derived 
from the \tempo_bpm setting, but it still seems problematic.

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, ...

... each with corresponding metronome mark indicators.

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?