+(ly:add-interface
+ 'trill-spanner-interface
+ "An accidental for trill pitch"
+ '())
+
+(ly:add-interface
+ 'rhythmic-grob-interface
+ "Any object with a duration. Used to determine which grobs are
+interesting enough to maintain a hara-kiri staff."
+ '())
+
+
+(ly:add-interface
+ 'spacing-options-interface
+ "Supports setting of spacing variables"
+ '(spacing-increment shortest-duration-space))
+