env '(0 1 100 1)))
  (let* ((start (seconds-&gt;samples beg))
         (end (+ start (seconds-&gt;samples dur)))
         (cr (make-oscil freq))
         (md (make-oscil (* freq mc-ratio)))
         (fm-index (hz-&gt;radians (* index mc-ratio freq)))
         (ampf (make-env index-env :scaler amp :duration dur)) 
         (indf (make-env index-env :scaler fm-index :duration dur))) 
    (run
      (loop for i from start to end do
        (outa i (* (env ampf) 
                   (oscil cr (* (env indf) 
    