io freq)) :length (+ 1 (- end beg))))
        (fm-index (hz-&gt;radians (* index mc-ratio freq))))
    (run
      (loop for i from beg to end do
        (outa i (* amp (oscil cr (* fm-index (oscil md (env skewf))))))))))

(with-sound () (fm 0 40000 100 .25 1.0 4.0 0 0 '(0 0 50 1 100 0) .02))
</pre>
-->

<!-- SND CASE -->
<pre class="indented">
(define (fm beg dur freq amp mc-ratio index)
  (let* ((start (seconds-&gt;samples beg))
	 (end (+ start (seconds-&gt;samples dur)))
	 (cr (make-oscil freq))
	 (md (ma