We can use the `emms-volume' package, as provided by the emms-volume.el file, to manipulate the volume.
The amount to use when raising or lowering the volume using the emms-volume interface.
This should be a positive integer.
If you feel like binding those two functions to global keys — don't do it or you'll miss the convenience of `emms-volume-minor-mode'. Instead, bind the following two commands to some keys that you like.
Raise volume and enable or extend the `emms-volume-minor-mode' timeout.
Lower volume and enable or extend the `emms-volume-minor-mode' timeout.
Example:
(global-set-key (kbd "C-c +") 'emms-volume-mode-plus)
(global-set-key (kbd "C-c -") 'emms-volume-mode-minus)
Whenever you use one of these keys or call these functions with M-x, Emms will be put into `emms-volume-minor-mode' for a short period defined by `emms-volume-mode-timeout'.
The timeout in amount of seconds used by `emms-volume-minor-mode'.
In this interval you can raise/lower the volume simply by pressing
+ or -, which will also reset the timer to its initial
value. So instead of pressing C-c + six times to increase volume
by six steps of emms-volume-change-amount, you would simply type
C-c + + + + + +.