Set BreathingSign direction in single-staff polyphony
\version "2.23.13"
upper = \fixed c'' { c2.-. \breathe d4-. | c2.-. \breathe d4-. }
lower = \fixed c' { a2.-. \breathe b4-. | a2-. \breathe d2-. }
\score { {
\partCombine \upper \lower
\section
<< \upper \\ \lower >>
} }
Measure 1 is good. Measure 3 is arguable. Measures 2 and 4 are problematic.