dulator-phase-incr (hz-&gt;radians (* freq mc-ratio)))
         (modulator-phase (* 0.5 (+ pi modulator-phase-incr)))
	 ;; (pi+incr)/2 to get (centered) sin after integration, to match pm case above
         (fm-index (hz-&gt;radians (* freq mc-ratio index)))  
	 ;; fix up fm index (it's a frequency change)
         (val 0.0)
         (modulation 0.0))
   (run
     (loop for i from beg to end do
       (setf modulation (* fm-index (sin modulator-phase)))
       (incf carrier-phase modulation)      
       ;