anchor.diff:    (:documentation "Class representing a musical event."))
   
   (defun event (&rest params)
  +  "Create an event, using the PARAMS as its keys/values."
     (let ((ev (make-instance 'event)))
       (labels ((accumulator (pairs)
                  (when (not (null (car pairs)))
  
positive.code:       ev)))
  
  (defun set-event-value (event slot value)
    (if (position slot *event-basic-parameters*)
        (funcall (fdefinition (list 'setf slot)) value event)
        (setf (getf (slot-value event 'other-params) (as-keyword slot)) value)))
  
  (defun get-event-value (event slot)
    (let ((slot (re-intern slot)))
      (if (and (fboundp slot)
               (eq 'standard-generic-function (type-of (fdefinition slot))))
  
negative.code: (defmethod keys ((item null))
    nil)
  
  (defun plist-set (plist key val)
    (if (getf plist key)
        (progn
          (setf (getf plist key) val)
  