Left: 100 bifurcation diagrams obtained from random variations of the lip parameters around the values given in Table 2, the plain red lines are the targets obtained from human performance. The dashed line on the bottom plot corresponds to the modified target. Top right: mouth pressure at Hopf bifurcation and slope calculated from 100 linear regressions performed on the stable sections of the 100 bifurcation diagrams, the red diamond corresponds to the red line in the left plot. Bottom right: Δf₀ and f₀ obtained from the 100 bifurcation diagrams, the plain red diamond correspond to the red line in the left plot. The empty red diamond corresponds to the modified target.