making fermata effect the MIDI output? tempo along bezier curves?

[Ted Walther]

When you see fermata in hymns, it almost always means "hold the note
longer, robbing the next note of some duration".  If you do the
durations explicitly, it messes up the meter and the printed sheet
music.  What would it take to get the fermata to show up in printed
music, but have it do the time-robbing in the MIDI output?

I'm thinking I'd like the duration of the fermata to be explicit, like
it is with partial; g4\fermata 5*16 as an example.  Then succeeding
notes would be robbed until the lost time was made up, with no note
being robbed of more than half its duration.

Is there already something like this?

It would be interesting to be able to set the tempo at various places,
and have lilypond alter the durations in midi output to match the bezier
curve generated by the tempo settings, so that at each place where the
tempo is set, the tempo is exactly at the setting.  Wonder what it would
cost to sponsor that...  I think this would help give a more "human"
feel.  And be nice to swap out curves; straight line curves, quartic
curves...

Ted

--
          It's not true unless it makes you laugh,                           
     but you don't understand it until it makes you weep.

Eukleia: Ted Walther
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Contact: 604-435-5787