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:     result))
  
  (defun play-test (item)
    (format t "Playing ~s at ~f.~%" item (/ (get-internal-real-time) internal-time-units-per-second)))
  
  (defparameter *event-output-function* 'play-test
  
negative.code: (defmethod keys ((item null))
    nil)
  
  (defun plist-set (plist key val)
    (if (getf plist key)
        (progn
          (setf (getf plist key) val)
  