;;;
;;; A very simple frequency modulation instrument
;;; (nando, Oct 14 '96)

(definstrument fm (start-time duration carrier-freq modulator-freq index amplitude
		   &key
		   (amp-env '(0 0 0.5 1 1 0)))
  (multiple-value-bind (beg end) (get-beg-end start-time duration)
    (let* ((carrier (make-oscil :frequency carrier-freq))
	   (modulator (make-oscil :frequency modulator-freq))
	   (envelope (make-env :envelope amp-env 
			       :scaler amplitude
			       :start-time start-time 
			       :duration duration)))
      (Run
       (loop for i from beg to end do
	     (outa i (* (env envelope)
			(oscil carrier (* index (oscil modulator))))))))))

;;; (with-sound() (fm 0 3 440 5 0.005 0.1))

;;; (with-sound() (loop for time from 0 by 1.1 
;;;		    for f from 10 by 10 below 150 
;;;		    with ae = '(0 0 0.1 1 0.9 1 1 0) do
;;;		    (fm time 1.2 440 f 0.1 :amp-env ae)))