+ (beamlet-default-length ,pair? "A pair of numbers. The first number
+specifies the default length of a beamlet that sticks out of the left hand
+side of this stem; the second number specifies the default length of the
+beamlet to the right. The actual length of a beamlet is determined by
+taking either the default length or the length specified by
+@code{beamlet-max-length-proportion}, whichever is smaller.")
+ (beamlet-max-length-proportion ,pair? "The maximum length of a beamlet,
+as a proportion of the distance between two adjacent stems.")