Drag the candidate along the vowel's first formant. The smooth line is a penalty that grows as the vowel drifts from the target μ. Flip bin it and the same penalty becomes a staircase — every value inside a step now scores the same, no matter where it actually fell. Narrow the steps and the staircase creeps back toward the curve.
If a penalty is that squared distance from μ, weighting it and reading it as a probability gives a familiar shape. Turn the weight up and the grammar grows fussy about the target; turn it down and it shrugs. The ticks are a handful of make-believe productions the law is trying to sit under.