;;; Frequency sweeping sine wave instrument

(definstrument sweep (start-time duration minfreq maxfreq amplitude
                      &key (bow 5.0))
  (multiple-value-bind (beg end) (get-beg-end start-time duration)
    (let ((s (make-oscil :frequency 0))
          (f (make-env :base bow :envelope '(0 0 1 1) :duration duration
                       :offset minfreq :scaler (- maxfreq minfreq))))
      (run
       (loop for i from beg to end do 
     (setf (frequency s) (env f))
	 (outa i (* amplitude (oscil s))))))))

;;; 20-20KHz sweep...
;;; (with-sound(:srate 44100)(sweep 0 10 10 20000 0.03 :bow 5))

;;; 20-20KHz sweep with aliasing...
;;; (with-sound(:srate 22050)(sweep 0 10 10 20000 0.03 :bow 5))

;;; 20-20KHz sweep with a lot of aliasing...
;;; (with-sound(:srate 8192)(sweep 0 10 10 20000 0.03 :bow 5))