ns (* index freq mc-ratio)))
	 (ampf (make-env '(0 0 1 1 10 1 11 0) :scaler amp :duration dur))
	 (sqsum 0.0))
     (do ((i start (+ i 1)))
         ((= i end))
       (let ((vol (env ampf))
             (pulse (* index (nxy1sin fm-modulator)))
             (sq (* index (square-wave pm-modulator))))
         (outa i (* vol (oscil fm-carrier pulse)))
         (outb i (* vol (oscil pm-carrier 0.0 sq)))
         (outc i sqsum)
         (outd i sq)
         (set! sqsum (+ sqsum pulse))))))

(with-sound (:clippe