-printed over a white background that follows the outline of the stencil,
-if the grob is visible. A number sets the thickness of the outline as a
-multiple of the staff-line thickness. For compatibility with former
-behavior (now available with @code{whiteout-box}) the value @code{#t} is
-treated as @code{3.0}. Usually @code{#f} by default.")
- (whiteout-box ,boolean-or-number? "If a number or true, the grob
-is printed over a rectangular white background to white-out underlying
-material, if the grob is visible. A number indicates how far the
-outline extends beyond the bounding box of the grob as a multiple of
-the staff-line thickness. Usually @code{#f} by default.")
+printed over a white background to white-out underlying material, if
+the grob is visible. A number indicates how far the white background
+extends beyond the bounding box of the grob as a multiple of the
+staff-line thickness. The @code{LyricHyphen} grob uses a special
+implementation of whiteout: A positive number indicates how far the
+white background extends beyond the bounding box in multiples of
+@code{line-thickness}. The shape of the background is determined by
+@code{whiteout-style}. Usually @code{#f} by default. ")
+ (whiteout-style ,symbol? "Determines the shape of the
+@code{whiteout} background. Available are @code{'outline},
+@code{'rounded-box}, and the default @code{'box}. There is one
+exception: Use @code{'special} for @code{LyricHyphen}.")