- (remove-layer ,integer? "The @code{Keep_alive_together_engraver}
-removes all @code{VerticalAxisGroup} grobs with a @code{remove-layer}
-larger than the smallest retained @code{remove-layer}. Set to
-@code{#f} to make a layer invisible to the
-@code{Keep_alive_together_engraver}, set to @code{'()} to have it not
-participate in the layering decisions.")
+ (remove-layer ,key? "When set as a positive integer, the
+@code{Keep_alive_together_engraver} removes all
+@code{VerticalAxisGroup} grobs with a @code{remove-layer} larger than
+the smallest retained @code{remove-layer}. Set to @code{#f} to make a
+layer independent of the @code{Keep_alive_together_engraver}. Set to
+@code{'()}, the layer does not participate in the layering decisions.
+The property can also be set as a symbol for common behaviors:
+@code{#'any} to keep the layer alive with any other layer in the
+group; @code{#'above} or @code{#'below} to keep the layer alive with
+the context immediately before or after it, respectively.")