I know we don't have this, and that tempo spanners have been requested before. I just wanted to know how you deal with it for the time being, especially in cases where simply using a text spanner and an additional tempo marking in an independent tempo variable doesn't work as expected, for example because a melody raises the new tempo, and a text spanner can't align with the new tempo marking. After a lot of fiddling, I got to this solution:
\override TextSpanner #'to-barline = ##t
\override TextSpanner.bound-details.left-broken.text = ##f
\override TextSpanner.bound-details.right-broken.text = ##f
\override TextSpanner #'(bound-details left text) = "accel."
\override TextSpanner #'(bound-details right text) = \markup { \transparent "t" \smaller \general-align #Y #DOWN \note #"4" #1 \upright "= 66"}
s2. s4\startTextSpan
s1
\once \hide Score.MetronomeMark
\tempo 4 = 66
s1\stopTextSpan
This gives as a result a perfectly aligned accel. with a new tempo marking. It's all quite manual, of course (note the transparent "t"!), but it gives the desired result. Do y'all use a better/more efficient approach?
Best regards,
Martín.
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