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

(definstrument am (start-time duration carrier-freq modulator-freq 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)(+ 1.0 (oscil modulator))))))))))

;;; (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
;;;		    (am time 1.2 440 f 0.1 :amp-env ae)))