Moving slur positions vertically
The vertical position of a slur can be adjusted using the positions property of … …- instead it selects what placement of the slur looks best, taking into account the parameter values. Positive values move the slur up, and are appropriate for notes with stems …
\relative c' { \stemDown e4( a) \override Slur.positions = #'(1 . 1) e4( a) \override Slur.… …positions = #'(5 . 0) e4( a) \stemUp \override Slur.positions = #'(-5 . -5) e4( a) \stemDown \revert Slur.positions e4( a) }