I used to have a nice multimedia keyboard with all the fancy volume buttons and even a calculator button. I never even noticed them being there until it grew too nasty to look at and I had to have it incinerated and I bought a new one. A normal, cheapish, office-grade keyboard. It dawned on me soon after. I'll have to change the volume by clicking on the tray icon and scrolling like a peasant in the middle ages. I decided to deal with it and soon found a viable solution
Run the Keyboard settings for Xfce
and add two new shortcuts for the following commands:
amixer set Master 5%+ amixer set Master 5%-
You can map it to any free shortcuts you have lying around. I mapped it to Alt+* and Alt+/ inspired by the standard mplayer volume shortcuts the first time I was doing it.
I later discovered this to be quite impractical with all the having to put the pizza down to fiddle with the volume, but I was so used to it at that point that I never got around to changing it. Even when setting it up on other computers later on, I still mapped it to the same impractical shortcuts and I still have to put my pizza down.
I could no longer put up with putting down the pizza and remapped the sound on all my computers to Ctrl+* and Ctrl+/ so that I can reach it with one hand.