anchor.diff:  
   (defun make-sound-output-sink (&key
                                    (buffer-duration 0.2)
  -				 buffer-size-in-samples
  +                                 buffer-size-in-samples
                                    (volume 1.0)
  -                                 (format :pcm-single-float))
  +                                 (format :pcm-single-float)
  +                                 (channels 2)
  +                                 (sample-rate 44100))
  +  (unless (eql channels 2)
  +    (error 'sound-format-error
  +           :format format
  +           :channels channels
  +           :sample-rate sample-rate
  +           :format-control "Non-stereo sound formats not supported."))
  +  (unless (eql sample-rate 44100)
  +    (error 'sound-format-error
  +           :format format
  +           :channels channels
  +           :sample-rate sample-rate
  +           :format-control "Non-44.1kHz sound formats not supported."))
     (make-instance 'sound-output-sink
                    :volume volume
                    :format format
  -                 :buffer (make-array (or buffer-size-in-samples (* (truncate (* 44100 buffer-duration)) 2))
  +                 :buffer (make-array (or buffer-size-in-samples
  +                                         (* (truncate (* 44100 buffer-duration)) 2))
                                        :element-type 'single-float)
                    :buffer-empty t
                    :buffer-head 0
  
positive.code: (defmethod (setf sink-volume) :around (value (sink sound-output-sink))
    (check-type value single-float)
    (call-next-method))
  
  (defvar *cards* '())
  
  
negative.code: ;;;; Copyright (c) 2017 Henry Harrington <henry.harrington@gmail.com>
  ;;;; This code is licensed under the MIT license.
  
  ;;; The interface that all sound device drivers must conform to.
  
  (defpackage :mezzano.driver.sound
    (:use :cl)
  