Document \breakDynamicSpan

[Reinhold Kainhofer]

With 2.13.x we added \breakDynamicSpan to allow lilypond to break a text 
dynamic spanner prematurely (while the cresc/decresc for MIDI-purposes still 
lasts until the \! or the next dynamic sign).
The purpose of this is to allow 1) Two subsequent dynamic signs above and 
below the staff and 2) to prevent excessive up-shifting of dynamics on a very 
high note (in particular since text dynamic spanners don't show any spanner 
line, intermediate high notes should not shift up the "cresc.", which happens 
by default, though).

Cheers,
Reinhold
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Reinhold Kainhofer, address@hidden, http://reinhold.kainhofer.com/
 * Financial & Actuarial Math., Vienna Univ. of Technology, Austria
 * http://www.fam.tuwien.ac.at/, DVR: 0005886
 * LilyPond, Music typesetting, http://www.lilypond.org