il freq))
	 (ampf (make-env '(0 0 1 1 10 1 11 0) :scaler amp :duration dur))
	 (sumex 0.0)
	 (fm-index (hz->radians (* index freq))))
     (do ((i start (+ i 1))
          (x 0.0 (+ x .0001)))
         ((= i end))
       (let ((vol (env ampf))
             (ex (- (random 2.0) 1.0)))
         (outa i (* vol (oscil fm-carrier (* fm-index ex))))
         (outb i (* vol (oscil pm-carrier 0.0 (* index sumex))))
         (outc i ex)
         (outd i sumex)
         (set! sumex (+ sumex (* fm-index ex)))))))

(wit