4 Proportional notation can be created by setting {proportionalNotationDuration}. Notes will be spaced proportional to the distance for the given duration.
7 \paper { ragged-right = ##t }
11 \set Score.proportionalNotationDuration = #(ly:make-moment 1 16)
12 \new Staff { c8[ c c c c c] c4 c2 r2 }
13 \new Staff { c2 \times 2/3 { c8 c c } c4 c1 }