Emacs lisp code to increase/decrease system volume from within Emacs.

(defun inc-volume ()
  "Increase system volume."
 
  (interactive)
  (start-process "aumix" "*Messages*" "/usr/bin/aumix" "-v" "+10"))
 
(defun dec-volume ()
  "Decrease system volume."
 
  (interactive)
  (start-process "aumix" "*Messages*" "/usr/bin/aumix" "-v" "-10"))