5 Slurs can be forced to always attach to note heads.
10 \property Voice.Slur \set #'direction = #1
11 \property Voice.Slur \set #'attachment = #'(head . head)
12 g''16()g()g()g()d'()d()d()d
15 \paper { linewidth = -1. }
18 \notes\relative c \fragment